Natural Disaster Survey Report

July 1995 Heat Wave

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Weather Service, Silver Spring, Maryland
Front Cover: High, low, average, and normal temperatures for Chicago, Illinois, during the midJuly 1995 heat wave.
Natural Disaster Survey Report

July 1995 Heat Wave

December 1995

U.S. DEPARTMENT OF COMMERCE

Ronald H. Brown, Secretary

National Oceanic and Atmospheric Administration

Dr. D. James Baker, Administrator

National Weather Service

Dr. Elbert W. Friday, Jr., Assistant Administrator
ii

PREFACE

Heat kills by taxing the human body beyond its abilities. In a normal year, about 175 Americans

succumb to the demands of summer heat. Among the large continental family of natural hazards,

only the cold of winter—not lightning, hurricanes, tornadoes, floods, or earthquakes—takes a

greater toll. In the disastrous heat wave of 1995, more than 1,000 people died.

I would like to express my gratitude to the National Oceanic and Atmospheric Administration

(NOAA) Disaster Survey Team for their objectivity in producing this survey report on the

performance of the National Weather Service (NWS) during the July 1995 heat wave. I am

particularly grateful to the Centers for Disease Control and Prevention (CDC) for providing

valuable insight into the health aspects of the heat wave.

Elbert W. Friday, Jr.

Assistant Administrator

 for Weather Services

December 1995
iii

FOREWORD

This report on the "July 1995 Heat Wave" was prepared by the NOAA Disaster Survey Team

after numerous interviews and meetings with Federal, state, and local officials in Chicago,

Illinois; Milwaukee, Wisconsin; Philadelphia, Pennsylvania; and St. Louis, Missouri.

Chicago and Milwaukee were selected due to the high heat-related death toll. Chicago

experienced its worst weather-related disaster, with 465 heat-related deaths recorded during the

period from July 11-27, 1995. Milwaukee also was severely affected, with 85 heat-related deaths

recorded during the same time period. Philadelphia and St. Louis experienced deadly heat waves

in 1993 and 1980, respectively, and were selected as complementary case studies.

The primary purpose of this disaster survey is to evaluate the performance of the NWS in

fulfilling its mission of providing timely and accurate warnings, watches, forecasts, advisories,

and statements during the July 1995 heat wave. NOAA and the NWS are dedicated to continuing

improvements in warning and forecasting for these events to provide local and state officials with

the lead time required to implement emergency heat response plans.

The team is grateful to the many individuals who took the time from their duties to share their

impressions of the events during the heat wave.

The Disaster Survey Team
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TABLE OF CONTENTS

Page

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

The July 1995 Heat Wave NOAA Disaster Survey Team . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

Findings and Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x

Chapter 1 Meteorological/Climatological Analysis ......................................1

Chapter 2 Health Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Chicago, Illinois . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Milwaukee, Wisconsin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Chapter 3 Provision of NWS Products and Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Chicago, Illinois . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Milwaukee, Wisconsin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Chapter 4 Communication, Emergency Preparedness, and Community

Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Chicago, Illinois . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Milwaukee, Wisconsin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Chapter 5 Case Studies in Heat Wave Preparedness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Philadelphia, Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

St. Louis, Missouri . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Appendix A Review Criteria for NWS Products, Services, and Actions . . . . . . . . . . . . . . . . . . . . A-1
v

ACRONYMS

CDC Centers for Disease Control and Prevention

CDT Central Daylight Time

F Fahrenheit

MIC Meteorologist in Charge

NOAA National Oceanic and Atmospheric Administration

NWR NOAA Weather Radio

NWS National Weather Service

NWWS NOAA Weather Wire Service

OLR Outgoing Long-Wave Radiation

SSI Surface Systems Incorporated

WCJIS Wisconsin Criminal Justice Information System

WCM Warning Coordination Meteorologist

WSH Weather Service Headquarters

WSOM Weather Service Operations Manual
vi

GLOSSARY

Advisory An Advisory is issued for less serious conditions that cause significant inconvenience

and, if caution is not exercised, could lead to situations that may threaten life and/or

property.

Extended Forecast As part of a State Forecast, an Extended Forecast is valid for the third through fifth

days after issuance.

Outlook An Outlook is used to indicate a hazardous event may develop. It is intended to

provide information to those who need considerable lead time to prepare for the

event, typically 48 hours or more in advance.

Short Term Forecast The Short Term Forecast can be valid up to 6 hours after issuance. For fast-breaking

or convective situations, however, the valid time may be less, such as 1 to 2 hours

after issuance.

Statement Issued at frequent intervals, Special Weather Statements amplify warnings, watches,

and advisories by reinforcing the message, indicating what is expected, and outlining

appropriate response actions. During active weather, they should be issued more

frequently to highlight existing conditions and how they might change in time. At

forecaster discretion, Severe Weather Statements may be issued to heighten

awareness and provide additional information for life-threatening conditions.

State Forecast The same as a Zone Forecast (see below) except for part or all of a state and with

additional extended forecast information.

Warning A Warning is issued when a hazardous event is occurring, is imminent, or has a very

high probability of occurrence. A Warning is used for conditions posing a threat to

life or property.

Watch A Watch is used when the risk of a hazardous event has increased significantly, but

its occurrence, location, and/or timing is still uncertain. It is intended to provide

enough lead time so those who need to set their plans in motion can do so, typically

12 to 36 hours in advance.

Zone Forecast Zone Forecast is valid up to 36-48 hours after issuance. Periods within the forecast

are usually 12 hours long. The first 12 hours, however, may be divided into subperiods, usually 6 hours long.
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THE JULY 1995 HEAT WAVE

NOAA DISASTER SURVEY TEAM

After a significant weather event, such as a heat wave, a disaster survey team may be assigned by NOAA to

evaluate the role played by the NWS, provide an objective appraisal, and make findings and recommendations.

Team Members

Leader, Dr. Kathryn D. Sullivan, NOAA Chief Scientist.

Technical Leader, Eugene P. Auciello, Service Implementation Manager, Office of Meteorology, Weather

Service Headquarters (WSH).

Coordinator/Editor, Linda S. Kremkau, Technical Analyst, Customer Service, Office of Meteorology, WSH.

Dr. Christopher R. Adams, Sociologist, Cooperative Institute for Research in the Atmosphere, Colorado State

University.

John Feldt, Meteorologist in Charge (MIC), NWS Forecast Office, Des Moines, Iowa.

Michael Franjevic, Warning Coordination Meteorologist (WCM), NWS Forecast Office, Phoenix, Arizona.

Randee Exler, Chief, NOAA/NWS Office of Public Affairs, WSH.

Dr. Annemarie Wasley, Epidemic Intelligence Service Fellow, National Center for Environmental Health, CDC.

Dr. Robert E. Livezey, Meteorologist, Climate Analysis Center, National Meteorological Center.

Dr. William H. Hooke, Program Director for Weather Research, NOAA Office of Oceanic and Atmospheric

Research.
viii

EXECUTIVE SUMMARY

Extreme heat may be one of the most underrated and least understood of the deadly weather phenomena. In

contrast to the visible, destructive, and violent nature associated with "deadly weather," like floods, hurricanes,

and tornadoes, a heat wave is a "silent disaster." Unlike violent weather events that cause extensive physical

destruction and whose victims are easily discernible, the hazards of extreme heat are dramatically less apparent,

especially at the onset.

During the 3-day period from July 13-15, 1995, approximately 70 daily maximum temperature records were set at

locations from the central and northern Great Plains to the Atlantic coast. The July 1995 heat wave at Chicago

and Milwaukee was a highly rare and, in some respects, unprecedented event in terms of both unusually high

maximum and minimum temperatures and the accompanying high relative humidities. Chicago experienced its

worst weather-related disaster, with 465 heat-related deaths recorded during the period from July 11-27. 

Milwaukee was also severely affected, with 85 heat-related deaths recorded during the same time period. The

number of deaths in Chicago and Milwaukee exceeds the average number of lives lost each year in the United

States to all floods, hurricanes, and tornadoes.

Large urban areas pose unique problems during excessive heat situations. Without the extent of urbanization in

Chicago and Milwaukee, the July 1995 heat wave might have been outstanding rather than unprecedented. There

is sufficient circumstantial evidence to conclude that the urban heat island was at least partially responsible for

the severe conditions in Chicago’s south side. In fact, the elderly and infirm residing in urban areas are in the

greatest danger during heat waves.

Because of its nature, heat waves are easier to predict than more short-lived and highly localized weather events

like tornadoes. In both Chicago and Milwaukee, NWS issued accurate warnings of the developing heat wave

several days before it arrived, and these messages were quickly broadcast by the local media. Consequently, it

might be argued that given this advance warning, many, if not all, of the heat-related deaths associated with this

event were preventable. Unfortunately, a heat wave connotates discomfort, not violence; inconvenience, not

alarm.

Despite timely NWS warnings, forecasts, advisories, and statements and effective media coverage of the event,

this information either failed to reach or was not used effectively by the people who could have prevented heatrelated deaths. This group of people includes the victims themselves, many of whom were isolated elderly. 

Because of their isolation, they are very difficult to reach by any mechanism. However, the group also includes

the care providers for the victims as well as other persons in the communities. While these people may have been

made aware of the heat emergency, it seems clear that they did not comprehend the potential health impact for

those at risk.

City officials had neither the experience nor emergency response capabilities to translate the physical

characteristics of the heat wave into human impact. Both Chicago and Milwaukee had extensive disaster 
ix

preparedness plans for responding to more dramatic events, like floods or blizzards, but neither city possessed a

well-developed plan for responding to heat emergencies. One reason for the general unpreparedness of the

communities affected by the July heat wave was that neither local officials nor the community at large recognized

the potentially lethal nature of extreme heat. In both Chicago and Milwaukee, extreme heat was initially viewed

more as an inconvenience than as a public health emergency or disaster. While public health officials made

efforts to mitigate the impact of the heat wave within their communities, neither city was prepared to respond to

the heat emergency as a citywide disaster.
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FINDINGS AND

RECOMMENDATIONS

The following findings and recommendations are grouped by subject matter and are found within their

appropriate chapters as indicated.

Meteorological/Climatological Analysis

Finding: The July 1995 heat wave at Chicago and Milwaukee was a highly rare and, in some respects,

unprecedented event in terms of both unusually high maximum and minimum temperatures and the

accompanying high relative humidities.

Finding: The principal cause of the July 1995 heat wave was a slow-moving, hot, and humid air mass produced

by the chance occurrence at the same time of an unusually strong upper-level ridge of high pressure and

unusually moist ground conditions.

Finding: Long-term processes played no obvious role in the July 1995 heat wave. Given current forecasts

skills, there is no reason to believe increased risk of the event could have been anticipated more than a week in

advance or can be expected in the future.

Finding: The July 1995 heat wave was exacerbated by local effects, including urbanization. This effect was

especially notable in Chicago.

Health Impacts

Finding: One of the difficulties with measuring the mortality associated with a heat emergency is the lack of

definition for a heat-related death that is both standardized and practical. A standard definition for heat-related

death, such as the one used in Chicago, should be developed and adopted for national use by all medical

examiners.

Finding: The awareness of heat-related deaths by local medical examiners in Chicago and Milwaukee in 1995

led to the initial recognition in those cities of excess deaths during heat-wave periods.

Finding: In Chicago and Milwaukee, the people most affected by the heat were the elderly.

Recommendation: Since the elderly in urban areas are in the greatest danger during heat waves, the NWS must

proactively focus heat preparedness efforts toward this group.

Finding: Heat waves are not clearly recognized as public health emergencies.
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Recommendation: Emergency response organizations at the Federal, state, and local levels should be

encouraged to recognize severe heat waves as potential natural disasters, and areas at risk should be prompted to

develop emergency response plans for severe heat waves. These plans should target the groups most often

affected by the heat, including elderly persons, particularly those living alone; persons with chronic medical

conditions, especially cardiovascular or pulmonary disease; and persons taking psychotropic medications.

Recommendation: The analysis of morbidity during the July 1995 heat wave in Chicago and Milwaukee should

be investigated by public health officials in order to provide useful public health information about the

relationship of morbidity to mortality.

Finding: The vulnerability of the elderly in urban core areas was underestimated during the heat wave.

Recommendation: Forecasters should target Heat Warnings, Watches, Advisories, and Statements to those

groups that are most vulnerable.

Provision of NWS Products and Services

 Chicago, Illinois

Finding: The Extended Forecast Product issued by forecasters at the Chicago NWS Forecast Office

communicated the likelihood of high levels of heat and humidity 48 hours prior to the event.

Finding: Extended range forecasts of temperatures were generally within 3 to 5 degrees for high temperatures

and 5 to 7 degrees for low temperatures.

Finding: NWS forecasters at the Chicago Forecast Office communicated a forecast calling for high heat and

humidities 36 to 48 hours prior to the event.

Finding: Short-range temperature forecasts had state of the art accuracy. High temperature forecasts were

accurate to within 3 degrees. Low temperature forecasts were accurate to within 6 degrees. Both were

underestimates.

Finding: Forecasters used descriptive terminology, such as "muggy" and "humid," to communicate important

weather information.

Finding: A Heat Outlook or Heat Watch was not issued as allowed for in WSOM Chapter C-44, NonPrecipitation Weather Hazards.

Recommendation: The NWS should ensure that forecasters at all field offices understand the flexibility

provided by WSOM Chapter C-44 to issue a variety of critical information products on heat-related issues.
xii

Enhancement Concept 1: Stress the dangerous nature of excessive heat in NWS

Enhancement Concept 2: Keep a pulse on the community.

Finding: NWS forecasters at the Chicago Forecast Office issued accurate Short Term Forecasts that included

temperature, humidity, and heat index levels.

Finding: Heat Advisories were issued prior to and during the excessive heat event.

Finding: The initial Heat Advisory issued at 3:30 p.m., CDT, July 12, was issued under an incorrect product

title (Public Information Statement). A Non-Precipitation Weather Warning should have been issued.

Finding: NWS-issued forecast products contained highly detailed and accurate meteorological information,

including the heat index, but lacked call to action statements. Heat Advisories were the only products that

contained information relating to the potential impact of anticipated weather conditions or call to action

information.

Recommendation: Forecasters should focus on the health hazards associated with heat in warnings, watches,

forecasts, advisories, and statements. All products should include call to action statements.

Recommendation: MICs and WCMs at all NWS forecast offices should work with state, city, and local health

officials to determine threshold values for dangerous heat index levels tailored to their area.

Potential For Enhanced Service

Although the excessive heat was well forecast by forecasters at the NWS Forecast Office at Chicago, there are

several ways in which service to the public could have been enhanced.

With forecast or actual temperatures near 100EF, dew points near 80EF, and heat index levels above 110EF, the

seriousness of these weather conditions could have been stressed in Warnings, Watches, Advisories, and

Statements.

It was nearly impossible for forecasters to learn of the increasing heat-related deaths until after the peak period of

temperature. The earliest indication of a developing crisis was an enormous increase in emergency room

admissions. At one point, 18 Chicago-area hospitals were in bypass or unable to admit more people into the

emergency room. This occurred relatively early in the event. During times of excessive heat, forecasters should

establish contact with public health officials to obtain this information.
xiii

Enhancement Concept 3: Understand local problems of the community.

Enhancement Concept 4: Develop local studies for the community.

Enhancement Concept 5: Keep the community well informed.

Enhancement Concept 6: Work with commercial service providers.

Early indications suggest that the elderly in urban areas were vulnerable to the excessive heat. Forecasters

should issue targeted products addressed to the most vulnerable.

In some cases, there are thresholds of temperature, humidity, and hence heat index at which heat-related

problems increase. Local studies, in cooperation with health officials, could better define these critical values. 

They will most likely vary from region to region and, perhaps, city to city.

Once forecasters target specific groups and critical threshold heat values, keep the community informed via

frequent statements.

Work with commercial service providers to develop a heat hazards training element for their radio and television

customers to improve the on-air delivery of forecast information to the public.

 Milwaukee, Wisconsin

Finding: The Extended Forecast Product issued by forecasters at the Milwaukee NWS Forecast Office clearly

communicated the likelihood of unusually high levels of heat 5 days prior to the event.

Finding: Extended range forecasts of temperatures were initially 6 to 10 degrees low in the 3- to 5-day range

but improved to within 2 degrees in the 1- to 2-day range.

Finding: Two Special Weather Statements were issued 40 hours prior to the event and contained call to action

information for the elderly and others at risk.

Finding: NWS forecasters at the Milwaukee Forecast Office clearly, effectively, and accurately communicated

a forecast calling for high heat and humidities 36 to 48 hours prior to the event.
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Enhancement Concept 1: Focus on the highest at-risk groups.

Finding: Short-range temperature forecasts were accurate. Initial errors in forecast accuracy improved to

within 2 or 3 degrees at least 24 hours prior to the onset of the heat wave.

Finding: Forecasters used descriptive terminology, such as "muggy" and "humid," to communicate important

weather information.

Finding: A Heat Advisory was issued for 2 consecutive days, providing local officials excellent planning

information.

Finding: NWS forecasters at the Milwaukee Forecast Office issued accurate Short Term Forecasts that included

temperature, humidity, and heat index levels.

Finding: Heat Advisories were issued prior to and during the excessive heat event.

Finding: Heat index levels were provided in the first period (first 6 hours) of the Zone Forecasts.

Finding: NWS-issued forecast products contained highly detailed and accurate meteorological information,

including the heat index.

Finding: NWS forecasters at the Milwaukee Forecast Office issued frequent Heat Advisories and Special

Weather Statements to keep the community well informed.

Finding: All warnings, forecasts, advisories, and statements were of high quality and contained accurate

forecast details, including heat index levels.

Recommendation: MICs and WCMs at all NWS forecast offices should work with state, city, and local health

officials to determine threshold values for dangerous heat index levels tailored to their area.

Potential For Enhanced Service

Although forecasters at the NWS Forecast Office at Milwaukee kept the community well informed on the heat

wave, there are a few ways in which service could have been enhanced.

Large urban areas pose unique problems during excessive heat situations. Forecasters are encouraged to provide

frequent statements targeted to the groups at higher risk; in this case, the elderly and infirm residing in urban

areas.
xv

Enhancement Concept 2: Keep a pulse on the community.

Enhancement Concept 3: Develop local studies for the community.

Enhancement Concept 4: Work with commercial service providers.

It was nearly impossible for forecasters to learn of the increasing heat-related deaths until after the peak period of

temperature. The earliest indication of a developing crisis was an enormous increase in emergency room

admissions. At one point, several Milwaukee-area hospitals were in bypass or unable to admit more people into

the emergency room. This occurred relatively early in the event. During times of excessive heat, forecasters

should establish contact with public health officials to obtain this information.

In some cases, there are thresholds of temperature, humidity, and heat index at which heat-related problems are

increased. Local studies, in cooperation with health officials, could better define these critical values.

Work with commercial service providers to develop a heat hazards training element for their radio and television

customers to improve the on-air delivery of forecast information to the public.

Communication, Emergency Preparedness, and Community Response

Finding: Despite timely NWS warnings, forecasts, advisories, statements, and effective media coverage of the

event, city officials had neither the experience nor emergency response capabilities to translate the physical

characteristics of the heat wave into human impact.

Recommendation: NWS offices should work with local officials to develop a public awareness and community

response plan for such events, especially among vulnerable or disadvantaged groups.

Finding: Media coverage of the July 1995 heat wave in Chicago and Milwaukee was substantial from both

meteorological and health angles.

Finding: Staff meteorologists at radio and television stations gave the NWS high marks for timely and accurate

forecasts and related services during the heat wave.

Finding: The Chicago and Milwaukee media have not developed a public response to heat hazards as they have

for other severe weather phenomena.
xvi

Recommendation: The NWS must enhance its public education campaign regarding the use of the heat index

and the dangers of heat. The media and the private sector should be enlisted as partners through professional

associations, such as the American Meteorological Society and the National Weather Association.

Finding: At the time of the July 1995 heat wave, the emergency preparedness program for extreme heat in

Chicago was organized and administered from the public health department, which was different from other

hazardous weather events.

Finding: Officials in Chicago did not realize the difference between NWS weather warnings and private sector

warnings.

Recommendation: The Chicago NWS Forecast Office should work with Chicago officials to provide user

training on NWS watch/warning products.

Finding: Chicago and Milwaukee officials and the public did not fully understand the heat index or the extent

of the threat from heat waves.

Recommendation: The NWS must enhance its community education campaign regarding the use of the heat

index and the dangers of heat.

Case Studies in Heat Wave Preparedness

Recommendation: NOAA should actively encourage other Federal agencies, such as the Department of Health

and Human Services, the Environmental Protection Agency, and the Federal Emergency Management Agency, to

join in research on excessive heat, mortality, and morbidity.

Recommendation: The NOAA Chief Scientist should convene a workshop comprised of interagency physical

scientists, private sector providers, social scientists, and epidemiologists to provide operational research

recommendations in light of the scientific advances made over the last decade. The relationship between heatrelated mortality and the heat index, as well as other proposed predictors of heat stress, should be simultaneously

evaluated to determine which method most accurately predicts the health consequences of a heat wave.

 Philadelphia, Pennsylvania

Finding: Philadelphia’s Heat Wave Preparedness Task Force developed an extensive and detailed plan for

responding to heat emergencies.

Finding: Philadelphia’s Heat Response Emergency Plan is activated by Heat Warnings issued by the NWS.
xvii

Finding: Emergency heat-related activities in Philadelphia are mobilized on the basis of predictions of an

alternative model developed by Professor Laurence Kalkstein, Center for Climatic Research, University of

Delaware.

Finding: It is not clear how much better the Kalkstein model compares with other models in predicting the

health effects of a heat wave.

Recommendation: The Kalkstein model should be reviewed after its proposed expansion to Chicago, Illinois,

and Atlanta, Georgia, in 1996.

Finding: NWS forecasters clearly, effectively, aggressively, and accurately communicated a forecast for the

Philadelphia area calling for dangerously high heat and humidities 36 to 48 hours prior to the event.

Finding: Recognizing the unique situation of an urban center, NWS forecasters issued a Heat Warning for

Philadelphia (the highest level possible) for a consecutive 2-day period. This action provided community

officials with key planning information.

Recommendation: NOAA should quantify the urban heat island effect to incorporate in NWS Heat Warnings,

Watches, Advisories, and Statements.

 St. Louis, Missouri

Finding: St. Louis’ Operation Weather Survival, a loose affiliation of agencies involved in responding to heat

emergencies and coordinated by the local chapter of the United Way, developed an extensive and detailed plan

for responding to heat emergencies.

Finding: The St. Louis Heat Response Plan is activated by Heat Warnings jointly issued by the St. Louis

Department of Health and the St. Louis County Health Department, based on readings of a wet bulb globe

thermometer not by Heat Warnings issued by the NWS.

Finding: NWS forecasters clearly and accurately communicated the likelihood of unusually high levels of heat

for St. Louis 5 days prior to the event.

Finding: NWS forecasters issued a Heat Advisory for St. Louis for a consecutive 2-day period. This action

provided community officials with key planning information.
xviii
xix
1

July

12 13 14 15 16 17

Chicago Midway Airport MAX 97 106 102 98 93

MIN 75 81 84 77 76

Chicago O’Hare Airport MAX 97 104 100 98 93

MIN 73 81 83 75 74

Milwaukee MAX 91 103 103 92 88

MIN 65 78 84 69 68

Philadelphia MAX 94 98 103 91 94

MIN 74 76 81 74 73

St. Louis MAX 100 101 99 98 96

CHAPTER 1

METEOROLOGICAL/CLIMATOLOGICAL

ANALYSIS

Major weather events, like the remarkable heat wave that blanketed major midwestern and eastern cities for

several days in mid-July 1995, are often the result of a number of meteorological and climatological factors that

operate on several different time and space scales. Sufficient evidence for this event is available to address

several key questions, among them the roles of longer term phenomena, like trend, or the El Niño/Southern

Oscillation system and the impact of urbanization. These issues will be discussed after the heat wave is first

placed in a historical context at Chicago as well as three other major cities: Milwaukee, Wisconsin; Philadelphia,

Pennsylvania; and St. Louis, Missouri. Chicago and Milwaukee were selected due to the high heat-related death

toll. Philadelphia and St. Louis, having experienced deadly heat waves in 1993 and 1980, respectively, were

selected as complementary case studies.

Historical Context

During the 3-day period from July 13 through 15, approximately 70 daily maximum temperature records were set

at locations from the central and northern Great Plains to the Atlantic coast. To examine just how unusual the

mid-July heat wave was at the four surveyed cities, the most readily available historical daily data set, maximum

and minimum temperatures and their averages, was utilized. Table 1 depicts a chronology of the heat wave at

each of the four cities over the appropriate 5-day period.

Table 1

Daily Maximum and Minimum Temperatures (EF)

for the mid-July 1995 Heat Wave
2

July

12-13 13-14 14-15

Maximum Temperature

Chicago O’Hare Airport (4) 2 (7)

 (38 years)

Chicago Midway Airport 5 1 9

 (48 years)

Chicago Official (123 years) (11) (3) -

Milwaukee (48 years) (17) 1 (11)

Philadelphia (48 years) - - (4)

St. Louis (48 years) - - -

Minimum Temperature

Chicago O’Hare Airport (12) 1 (3)

Chicago Midway Airport 13 1 (2)

Chicago Official - 4 (17)

Milwaukee - 1 5

Philadelphia - - (5)

St. Louis (20) (3) (6)

Average Temperature

Chicago O’Hare Airport (4) 1 3

Chicago Midway Airport 4 1 2

Chicago Official (13) 1 (11)

Milwaukee - 1 6

Philadelphia - - (3)

Table 2 shows the all-record ranks of the mid-July 1995 2-day mean maximum, minimum, and daily average

temperatures observed, respectively, for six records for the four cities. Over its long history, the official Chicago

record has been measured in a number of locations, including Midway Airport from 1942 to 1979 and O’Hare

International Airport from 1980 to present. Because high temperature extremes can occur from mid-May through

mid-September, each year there are 120 days in which there is an opportunity for a specific temperature to be

exceeded. Thus, a 40-year record represents about 4,800 opportunities, a 70-year record about 8,400, etc. These

counts help put into perspective rankings in table 2 and later in table 4. The table demonstrates that this year’s

event at Chicago and Milwaukee was at least highly rare and, in several respects in both of these cities, totally

unprecedented. To underscore this, one should note that the official average 2-day temperature of 92E Fahrenheit

(F) observed at O’Hare International Airport for July 13 and 14 was the highest in 123 years. The peak 2-day

period at Philadelphia was highly unusual for its 48-year record but not as outstanding as that for Chicago,

especially in light of the longer records for Chicago. St. Louis experienced highly unusual minimum

temperatures, but the mid-July ranks for 2-day mean maximum and average temperatures for its 48-year record

do not rank among the top 20. The principal reason for these differences will be apparent from the discussion in

the following sections. The relative severity of the heat wave between cities is also reflected in the daily

maximum temperature records set at the four locations in mid-July, which are listed in table 3.

Table 2

Rank (if in top twenty) of Mean Temperatures

for 2-day Periods in mid-July 1995 (ties in parentheses)
3

July

12 13 14 15

Chicago/O’Hare 97 104 100

Chicago/Midway 106

Milwaukee 101

Philadelphia 103

Table 3

Daily Maximum Temperature Records Set at 

Chicago, Milwaukee, and Philadelphia on July 12-15, 1995

(all-time daily maximum records in bold)

What ultimately distinguishes the 2-day period in mid-July at Chicago and Milwaukee from all others is the

combination of both unusually high maximum and minimum temperatures. The principal factor for the elevated

nighttime temperatures was the relatively high moisture content (i.e., humidity) in the air. Observed dew points,

a direct measure of the moisture content, were extraordinarily high on three straight nights at Chicago’s Midway

Airport. The accompanying relative humidities, well above 90 percent in the late evenings, added substantially to

the already considerable human stress implied by the high average observed temperatures. Data at several other

locations in the Chicago metropolitan area and on a larger regional scale confirm that these extraordinary levels

were largely a consequence of a very moist regional air mass but also may be partially attributable to additional

local effects at Chicago and perhaps some other midwestern locations.

Of some interest also is the extended period of high heat surrounding the 2 key days that have been emphasized

so far. Table 4 contains similar information as table 2 but for 3- to 5-day mean daily average temperatures. Data

for St. Louis are not tabulated since the ranks are not in the top twenty. Note that at Chicago, the mid-July event

still ranks first or second in all respects over the most recent 50 years but not when viewed from the perspective

of the long-term record. Ferocious heat waves, lasting 5 and 6 days and exceeding the 1995 heat wave, occurred

in 1911 and 1916, respectively. In contrast, conditions over 3- to 5-day periods in July 1995 at Milwaukee were

exceeded in August 1988.

Finding: The July 1995 heat wave at Chicago and Milwaukee was a highly rare and, in some respects,

unprecedented event in terms of both unusually high maximum and minimum temperatures and the

accompanying high relative humidities.
4

3-Day Mean

12-14 13-15 14-16

Chicago O’Hare Airport 2 1 5

 (38 years)

Chicago Midway Airport 2 1 4

 (48 years)

Chicago Official (123 years) 5 4 -

Milwaukee (48 years) 4 2 (20)

Philadelphia (48 years) NC (5) (12)

4-Day Mean

12-15 13-16 14-17

Chicago O’Hare Airport 1 (2) NC

Chicago Midway Airport 1 2 NC

Chicago Official 5 (6) NC

Milwaukee (3) (3) NC

Philadelphia NC (14) (16)

5-Day Mean

12-16 13-17

Chicago O’Hare Airport 1 NC

Table 4

Rank (if in top twenty) of Mean Daily Average Temperatures

for 3- to 5-day Periods in mid-July 1995

 (ties in parentheses)

("NC" means not calculated)

Development of the Meteorological Event

The principal cause and origin of the heat wave is straight-forward—a slow-moving, hot, and humid air mass

(figure 1) was produced by a very strong upper-level ridge of high pressure. This ridge originated as an

amplification of the climatologically normal weak ridge which exists in the western United States in July. Its

growth was a downstream adjustment of the westerly winds to a major weather disturbance affecting the

subtropical ridge in the western Pacific Ocean several days before.

This sequence of events can be followed clearly in the series of 5-day mean charts in figures 2 and 3 which filter

out day-to-day fluctuations. The pair of charts in figure 2 shows departures from normal of outgoing long-wave

radiation (OLR), which are good proxies of anomalous rainfall and latent heating of the atmosphere in the tropics

and subtropics. A significant flare-up of this heating off the coast of east Asia extending out into the Pacific is

indicated by a substantial increase in negative OLR anomalies between 
5

C Figure 1. Daily progression of the mid-July 1995 heat wave in terms of maximum

apparent temperatures (heat index) at least 105 F and minimum temperatures at least

78 F.
6
7

Figures 3a, 3b, 3c, 3d. Sequence of 5-day mean upper-level pressure and flow conditions leading up to and including the

heat wave. The lines depict the location of upper-level ridges and troughs of pressure in mid-latitudes and the colors

anomalies in the pressure. Upper-level westerly winds flow along the lines with jets located where the lines are most

closely spaced. The color scale indicates 500 millibars height departures from normal in meters.
8

Figures 3e, 3f, 3g, 3h. Sequence of 5-day mean upper-level pressure and flow conditions leading up to and including the

heat wave. The lines depict the location of upper-level ridges and troughs of pressure in mid-latitudes and the colors

anomalies in the pressure. Upper-level westerly winds flow along the lines with jets located where the lines are most

closely spaced. The color scale indicates 500 millibars height departures from normal in meters.
9

the last week of June and the first week in July. This flare-up was accompanied by an increase in

convection in the tropics to the south as well. However, this fact should not be taken as evidence that the

tropical disturbance was the cause of the subtropical disturbance. The flow in the tropics (not shown)

was not that expected in situations where a tropical rainfall anomaly is the source of a convective

outburst to the north.

The upper-air flow and departures from normal of heights of the 500 millibar pressure surface, which

correspond to ridges and troughs of pressure at a fixed upper level, for the time periods in figure 2 are

shown in figures 3a and 3b, respectively. Note the increase in strength of the western Pacific ridge,

indicated by the increase in the positive height anomaly between the two periods. This amplification

continued for a few more days (figure 3c) and led immediately to a downstream flow adjustment across

the entire north Pacific basin, which culminated several days later with enormous amplification of the

western U.S. ridge (figures 3c, 3d, and 3e). The latter’s slow eastward progression across the middle of

the country, with the most anomalously high upper-air pressures across the northern half of the United

States, can be followed clearly in figures 3c, 3d, 3e, 3f, 3g, and 3h. Apparent in the last two maps is that

the maximum upper air height anomaly (and its attendant implications for heating of the atmosphere from

sinking air and solar radiation) occurred as the anomaly passed over Lake Michigan (figure 3g); the

anomaly subsequently lost strength as it moved into the mid-Atlantic region (figure 3h).

The trajectory of this anomalous feature (passing to the north of St. Louis, and its relative strength,

strongest near Chicago and Milwaukee and a little weaker over Philadelphia) provides much of the

explanation for the contrast in the uniqueness of the heat wave event at the four cities. The slow

movement of the structure provided ample opportunity for the day by day heating, accumulation of

moisture, and transport into the upper midwest, and later into the east, of the air necessary to produce the

extreme conditions observed.

The occurrence of the unusually strong large-scale structure that led to the mid-July heat wave appears to

have been the result of a complicated chain of events, whose initiation, the flare-up in the western

Pacific/east Asia region, can be characterized as random. In this context, something resembling the

structure could not have been predicted more than a week in advance. Of course, as illustrated below,

both regional and local factors likely played roles in the conditions ultimately experienced in Chicago,

Milwaukee, and possibly other locations. These factors only complicate the prediction problem further.

To understand the high water vapor content (dew points in the range of 75-80E+F) of the portion of the

air mass that moved from Iowa, Missouri, and southern Minnesota through the lower Great Lakes into

Pennsylvania requires consideration of the surface air trajectories for several days preceding the arrival

of the air mass and the conditions of the surface over which it traveled. The sequence of surface weather

charts in figure 4 depicts a weak but steady surface flow from first the south and later the southwest into

the central Mississippi/lower Missouri Valleys region from as early as the evening of July 11 right up to

the climax of the heat wave. A chart of soil-moisture conditions less than a week before the peak of the

heat wave (figure 5) shows that the soil was quite wet for much of Kansas, Missouri, Iowa, and Illinois

over which the air traveled. Moreover, the air originating or moving into and through this four-state area

already carried dew points in the high 60s and lower 70s (figures 4a and 4b).
10

Figure 4. Early evening surface winds and water vapor contents (in terms of dew points in EF) for 5 consecutive days in

mid-July 1995 at locations throughout the eastern United States. The former are generally light in the Midwest and

Northeast. Values of the latter in excess of 75EF (green shades) can be considered unusually high.
11

Figure 5. Soil moisture conditions less than 1 week before the onset of the heat wave. The ground over

which the hottest part of the air mass moved was quite wet.
12

Thus, it is not surprising that, with the intense solar insolation and its potential for evaporation of water

vapor accompanying the approaching mammoth upper-air ridge of high-pressure (figures 3f and 3g), a

tongue of air w

ith dew points in excess of 75EF had formed by the evening of July 12 (figure 4b). This area corresponds

closely to the region of pre-existing wet ground and contained a smaller area with dew points in excess of

80EF over eastern Iowa and southern Minnesota. This moisture-laden air spread mainly east, with its

center passing over Chicago, Milwaukee, and finally Philadelphia over the next few days (figures 4c, 4d,

and 4e) before moving offshore. Again, note that the core of the moistest air passed to the north of St.

Louis, providing additional explanation for the somewhat less relative severity for conditions in that city.

Finding: The principal cause of the July 1995 heat wave was a slow-moving, hot, and humid air

mass produced by the chance occurrence at the same time of an unusually strong upper-level ridge

of high pressure and unusually moist ground conditions.

Role of Long-term Factors

In this section, two factors—El Niño/Southern Oscillation and long-term trends—are examined that are

commonly associated with substantial departures from normal of surface conditions on monthly to

seasonal time scales. This is important because monthly average temperature records were set at both

Chicago and Philadelphia, and because some degree of predictability is implied when either factor is a

significant influence. Moreover, if either played a role, additional inferences can be made about future

vulnerability to similar events.

The link between climatic effects and El Niño is well established. The term "El Niño" has come to be

reserved for exceptionally strong warm intervals that raise the water temperature across the equatorial

Pacific. The term "Southern Oscillation" represents the ups and downs of the east-west seesaw in

southern Pacific barometric pressure which is linked to dramatic changes in the distribution of rainfall in

the tropics. The warm waters associated with El Niño and the pressure seesaw of the Southern

Oscillation are part of the same phenomena referred to as the El Niño/Southern Oscillation.

There is little support for El Niño/Southern Oscillation as a contributing mechanism for the heat wave. 

Tropical equatorial Pacific Ocean sea-surface temperature anomalies were quite small both prior to and

during the month of July, i.e., this was not an active El Niño summer. Additionally, recent studies that

have examined the El Niño/Southern Oscillation signal when the system is active show little or no

response for the upper-midwest or middle-Atlantic regions during the month of July.

The question of whether the monthly mean temperature records for July are symptomatic of longer term

trends needs to be addressed separately for Chicago and Philadelphia. Note in figure 6 that the historical

temperature ranks for July 1995 of the multistate regions encompassing the eastern seaboard are quite

high, while those for the two regions covering the Ohio and upper Mississippi River Valleys are not even

in the upper quintile. Further, note in figure 7 that this same regional contrast is reflected on average

over the previous ten summers (i.e., the Atlantic coast has been quite warm on the average, while the

Midwest has been cool or near normal). The former probably reflects an enhanced 
13

Figure 6. Historical rank of July 1995 average temperature by region and Nation. The month overall was

exceptionally warm along the eastern seaboard but not unusually so in the Midwest.
14

Figure 7. Average summertime (June, July, and August) departures from

normal temperature (o

F times 10) for the 10 years preceding the summer of 1995. 

Note that recent trends around Lake Michigan have been for normal or slightly

below normal temperatures but along the mid-Atlantic coast for above normal

temperatures.
15

Bermuda high, which played no apparent role in the early to mid-July weather sequence described in the

previous section.

Thus, the mid-July synoptic event, though not necessarily related to some longer term process, reinforced

the 10-year tendency at Philadelphia but not at Chicago. Another argument against trend as an important

factor for Chicago is the fact that the nearest rivals for the 2-day July 1995 event, in terms of average

temperature, occurred in the summers of 1911 and 1916. In contrast, Philadelphia experienced a heat

wave as recently as July 1993 that in many respects substantially exceeded the severity of the July 1995

occurrence. The most reasonable conclusion is that the July 1995 heat wave in Chicago was the result of

a rare juxtaposition of an exceptionally strong upper-air ridge and unusually wet July soil in the nearby

upstream air mass source region. Corollaries to this are that increased vulnerability to such a

meteorological event could not have been anticipated in late June, nor should necessarily be expected in

the future based on current information. Local effects, including urbanization, also may have played

enough of an additional role in Chicago to make the event unprecedented.

Finding: Long-term processes played no obvious role in the July 1995 heat wave. Given current

forecasts skills, there is no reason to believe increased risk of the event could have been anticipated

more than a week in advance or can be expected in the future.

Role of Microclimate Factors in Chicago

Conditions in the Chicago area differed from one location to another during the mid-July heat wave. 

This was already evident from table 1 which indicated more severe conditions at Midway Airport than

O’Hare. This and even more pronounced local differences will now be examined more closely to clarify

the role played by factors like the urban heat island, lake proximity, evapotranspiration, wind direction,

etc. 

For this survey, daily maximum and minimum temperature data at 11 locations in the Chicago

metropolitan area were available, of which nine were considered useable, either because of observation

times or credibility. In addition, detailed hourly observations at Chicago’s O’Hare International and

Midway Airports were available and proved enormously useful. The relative locations of these 11 sites,

along with other features mentioned below, are mapped in figure 8.

Daytime maximum temperatures on July 13 and 14 are listed in table 5 for all 11 locations. Three

locations with the highest maximum average temperature for the 2 days (the first three listed)—the two

airports and Chicago Botanic Gardens—have two things in common. These locations are the three

observation sites closest to downtown Chicago, Midway being the closest, followed by O'Hare, and the

Botanic Gardens. They are three of the four points listed that are closest to Lake Michigan, with the

Botanic Gardens adjacent to the lake, Midway somewhat inland, and O'Hare another several miles

inland. Waukegan is also on Lake Michigan.
16

July

13 14

Midway Airport 106 102

Botanic Gardens 105 102

O’Hare Airport 104 100

Joliet 103 101

Aurora 102 100

Lake Villa 102 100

Waukegan 102 100

McHenryville 101 100

Park Forest 102 99

Elgin 101 98

Figure 8. Locations of key features and observing sites in and near

Chicago.

Table 5

Maximum Temperatures (EF) for the Chicago Metropolitan Area

on July 13 and 14, 1995
17

July

13 14

Midway Airport 81 84

O’Hare Airport 81 83

Lake Villa 77 81

Romeoville 77 78

July

13 14 15

Midway Airport 81 (81) 84 (83) 83 (83)

O’Hare Airport 81 (77) 83 (79) 79 (78)

Waukegan 78 83 78

Botanic Gardens 78 82 78

Joliet 73 78 79

Elgin 71 80 78

Park Forest 73 80 76

The contrast between close-in locations and sites more distant from Chicago’s Loop is again apparent in

table 6 which contains minimum temperatures for the two calendar, 24-hour periods (i.e., observations

taken at midnight) at three points where they were reported as such and the two airports where hourly

data were available. These tables contain sufficient circumstantial evidence to conclude that the urban

heat island was at least partially responsible for the severe conditions in Chicago’s south side (near

Midway Airport), but other factors, like advective effects, locally strong evapotranspiration, and

proximity to Lake Michigan, cannot be completely discounted as additional microclimatic influences.

Table 6

Minimum Temperatures (EF) for the Chicago Metropolitan Area

on July 13 and 14, 1995

Additional clues as to whether any of these other factors (just mentioned) affected nighttime

temperatures are contained in table 7, which lists minimum temperatures from the 24 hours prior to early

morning observation times (ranging from 6 a.m. to 8 a.m., local time). Again, Midway stands out on all

three of the evenings, while O’Hare, Botanic Gardens, and Waukegan are noticeably warmer on the

evenings of July 13 and 14.

Table 7

Minimum Temperatures (EF) and Maximum Dew Points (EF) (in parentheses)

for the Chicago Metropolitan Area for the 24 Hours 

Preceding Morning (6 to 8 a.m.) Observation Times

on July 13-15, 1995
18

During the critical period, peak winds were mostly from the south and southwest, so one explanation for

the high minima at the Botanic Gardens and Waukegan is that they were downwind of the city core, at

least much more so than any other sites. This factor was strongest on the evening of July 12, less so on

the evening of July 13, and least so on the evening of July 14, as the winds shifted from the south to

dominantly southwest. The overall decrease in the difference in minima between the two lakeside

stations and the other four locations (excluding the airports) from the evening of July 12 through the

evening of July 14 is consistent with this wind shift. Nevertheless, winds were also generally quite light,

so it is not implausible that Lake Michigan served as an additional source of water vapor for observation

sites next to it. The light winds also imply reduced surface mixing of the lake water and the possibility of

surface water temperatures well above normal. Moreover, as the winds shifted from more southerly to

more southwesterly, lake proximity would have had less relative impact, again consistent with the trend

of the differences in minima between the Botanic Gardens and Waukegan and four other locations well

removed from both the lake and the city core. 

Maximum dew points are also listed for the two airports in table 7, while the minima at the other six sites

serve as approximate upper bounds for the dew points there. Dew points at Midway Airport turn out to

be substantially higher than those recorded at O’Hare. In view of prevailing wind directions, it is

doubtful that Lake Michigan was an important source of moisture for Midway, so an additional source of

water vapor needs to be identified. One appealing candidate is heavy evapotranspiration over the nearby

Palos Forest Preserves, with its extensive woods and many sloughs located south and west of

Midway—i.e., upwind of Midway—during much of the heat wave. This idea is consistent with

attribution of the high minima at the lakeside locations also to downwind advective processes.

Clearly, these data are insufficient to resolve clearly the extent to which certain microclimatic factors

contributed to the highly severe conditions in south Chicago. However, they provide sufficient evidence

to support a role for local effects, particularly for an urban heat island effect. Without the extent of

urbanization in Chicago, the mid-July heat wave might have been quite outstanding rather than

unprecedented.

Finding: The July 1995 heat wave was exacerbated by local effects, including urbanization. This

effect was especially notable in Chicago.

Conclusions

The mid-July heat wave that brought unprecedented conditions to Chicago and Milwaukee, dangerous

conditions to Philadelphia, and harsh (but often observed) conditions to St. Louis was mainly a result of

the fortuitous juxtaposition of two important factors, namely a very strong, slow-moving upper-air ridge

of high pressure and a conveniently located source region of high soil moisture content. Chicago and

Milwaukee were ideally located to feel the full effects of this combination of factors. In at least Chicago,

near-record conditions were probably exacerbated to record conditions by local microclimatic factors,

including most certainly urbanization. The genesis and form of the event suggest that it was a weather

event whose occurrence, or probability of occurrence, is not easily related to longer term processes, like 
19

El Niño/Southern Oscillation or climatic trends. At this time, the occurrence or probability of such an

event probably cannot be forecast beyond the theoretical limit of dynamic predictability of 2 weeks, or

practically not currently beyond about 1 week.
20
21

CHAPTER 2

HEALTH IMPACTS

During and immediately following the heat wave, increased numbers of deaths, many of them attributed

directly to the heat, were reported in both Chicago and Milwaukee. There were 465 heat-related deaths

recorded for the Chicago area alone (CDC, 1995). This exceeds the average number of lives lost each

year in the United States to all floods, hurricanes, and tornadoes.

Methods

In both Chicago and Milwaukee, the first indication of the magnitude of the health effects of the heat

wave came from the medical examiner’s office, where bodies that had been found dead in overheated

dwellings began to be delivered on approximately the second day of the heat wave. While information

about deaths reported by the medical examiner provided a rapid indicator of a potential problem, such

information must be interpreted carefully because only 20 percent of deaths are usually seen by medical

examiners, and these deaths are not normally representative of the whole population. However, when a

severe heat wave occurred in Philadelphia in July 1993, a retrospective review of the death certificates

for that period found that of the approximately 110 certificates, which listed a heat-related cause or

condition, more than 90 percent of them had been included in the initial reports from the Philadelphia

Medical Examiners’s Office. This suggests that, for heat-related deaths, medical examiner data provides

a rapid and sensitive indicator.

Definition of Heat-related Death

One of the difficulties in measuring the mortality associated with a heat emergency is the lack of

definition for heat-related death that is both standardized and practical. Using the strict definition of

hyperthermia as the basis for classifying deaths requires that a core body temperature of 105EF or above

be measured at the time of, or immediately following, death. However, deaths frequently occur that,

judging by the circumstances of death, are clearly heat related but a core body temperature is either

unavailable or not meaningful (because the body was not discovered until hours or days after death) and

which, thus, cannot be strictly called hyperthermia deaths. Because of the obvious insensitivity of the

strict definition given above in these types of situations, the medical examiners of several cities

(including the four visited in this assessment) use a less restrictive definition for heat-related deaths that

allows them to include those deaths which, while not meeting the body temperature criteria, are judged to

be heat related on the basis of circumstantial evidence.

 
22

The Medical Examiner of Cook County, Illinois, who is responsible for investigating deaths occurring in

Chicago, classified deaths as being heat related if any of the following conditions were met:

< a body temperature of 105EF or above was measured at/shortly after the time of death; or

< evidence of high environmental temperature in the place where the body was found was noted by

rescuers; or

< the body was found in a decomposed state and was last seen alive at the time of the peak of the

heat wave.

Similar definitions are used by the medical examiners in Milwaukee, Philadelphia, and St. Louis. 

However, not all medical examiners use this definition. Consequently, it is difficult to compare the

numbers of heat-related deaths from one city to another or from one heat wave to the next. It is

recommended that a standard definition for heat-related death, such as the one used in Chicago, be

developed and adopted for national use.

 Chicago, Illinois

Heat waves and heat-related deaths are not new to Chicago. In 1988, there were at least 77 heat-related

deaths. However, when on July 12, 1995, the NWS predicted a maximum heat index of greater than

100EF for the following day and issued a Heat Advisory, few people considered it a potential medical

emergency. Even the Chicago Department of Health, which had been monitoring the weather and had

recommended that people modify their behavior because of the heat, expected that only a few people

would experience anything more than discomfort as a result of the hot weather. The first indication of

trouble came when the Chicago Police Department and Chicago Medical Examiner reported increased

numbers of non-violent deaths throughout the city. In Cook County (which includes Chicago), there are

usually 65-70 deaths a day from all causes, of which 17-20 are seen by the medical examiner. On July 15

alone, 162 heat-related deaths were reported by the medical examiner’s office (figure 9). For the period

of July 12-27, a total of 465 heat-related deaths were recorded. In contrast, no heat-related deaths were

reported for the week of July 4-10.

At the same time that bodies were beginning to accumulate in the city morgue, hospitals were also being

inundated with people who had been affected by the heat. Some hospital emergency departments began

to turn away ambulances on July 12 because they had insufficient capacity to accept additional patients;

by July 14th, 18 hospitals were on "bypass status" (figure 10). During very busy periods when an

emergency room does not have the capacity to accept additional patients, the hospital may go on "bypass

status," referring all incoming ambulances to less busy facilities. A planned review of the emergency

room records from selected hospitals for the heat-wave period will provide information on the

characteristics of the people who became sick because of the heat. It will be particularly useful to the

public health community to compare the characteristics of those who became sick but recovered to those

who died to determine if, or how, the two groups differed. It also will be valuable to determine whether

the increase in heat-related 
23

Figure 9. Heat-related deaths, Maximum Temperature (Tmax) and Heat Index (HI),

Chicago, July 11-23, 1995. (As reported by the Office of the Medical Examiner.) 

Figure 10. Hospitals on bypass status, Maximum Temperature (Tmax) and Heat Index

(HI), Chicago, July 11-23, 1995.
24

illnesses (morbidity) preceded the increase in heat-related deaths (mortality) and, if so, whether such

information could be used to monitor developing heat emergencies.

Examining the characteristics of those whose deaths were classified as heat related, it was observed that

the people most often affected by the heat were the elderly, particularly those living alone. While only

15 deaths were recorded for people under 44 years of age, 101 deaths were reported for those between 65

and 74 years of age, and 222 deaths occurred among those over 74 years of age (figure 11). Looking at

these numbers relative to the proportion of the population made up by each age category, the danger to

the elderly becomes even more clear. The estimated risk of death for those under 45 for the period July

12 through July 27 was 20 per 100,000 persons. In contrast, the risk of death for persons 65 through 74

years of age was 53 per 100,000, and for those greater than 74 years of age, it was 183 per 100,000. 

Deaths occurred throughout the city, with a slight clustering on the south side. With a cumulative

mortality of 19 per 100,000, males were more often affected than females, whose risk of death was 14 per

100,000. Although more blacks died (229) than whites (216), the rates for the two races do not differ

significantly. Very few heat-related deaths (less than 6 percent of the total number of heat-related

deaths) occurred among Hispanics relative to their representation in the total population. The reason for

this is not clear, but it is speculated that strong community or family networks within Hispanic

communities may have played a protective role.

Chicago and Illinois health officials are working with investigators from CDC to better determine the

characteristics of the people who died during the heat wave, so that this information can be used in future

heat waves to better target preventive measures at persons at increased risk for heat-related illness or

death. In addition to the deaths that were directly attributed to the heat, it is likely, given the experience

in other heat waves, that there were additional unmeasured increases in cardiovascular deaths which can

be indirectly attributed to the heat; these excess deaths should also be determined to better estimate the

total health impact of the heat wave.

 Milwaukee, Wisconsin

With weather patterns similar to those of Chicago, heat waves are not unusual in Milwaukee either. A

1988 heat wave claimed 11 lives, and in 1936, which was a drought year, 529 deaths were attributed to

the heat. Other notable heat waves occurred in 1947, 1955, 1968, and 1970. These previous heat waves

led the city to develop contingency plans for responding to such events, and a Heat Task Force has been

in existence since 1986. Consequently, on the afternoon of July 12 when the NWS predicted heat index

values of up to 120EF in the Milwaukee area and issued a Heat Advisory, the members of the Task Force

were ready for action. They first met as a group on July 14. Agencies participating in the task force

included the American Red Cross, the Salvation Army, the Office of Emergency Government, the

Milwaukee Department of Health, and the public utility companies.

Despite what appeared to be a reasonably good level of preparedness, on the evening of July 14 (at about

the same time that excess deaths were beginning to be reported in Chicago) the Milwaukee County

Medical Examiner’s Office observed a higher number of deaths than usual, many of them obviously heat

related. From July 14 to 17, the 
25

Figure 11. Deaths by age, Chicago, July 12-27, 1995.

The age-specific risk of dying of a heat-related cause during the heat wave period (July 12-27, 1995) was calculated

by dividing the number of heat-related deaths reported for an age group during that period by the total number of

persons in that age group as recorded in the census.
26

Milwaukee County Medical Examiner reviewed 129 deaths (versus a normal average of 30 deaths for a

similar 4-day time period). Eighty-five (85) of these deaths were attributed to the heat, of which 30 were

classified as environmental hyperthermia (strict definition with measured core body temperature greater

or equal to 105EF). The other 55 deaths occurred among older persons with pre-existing conditions

where circumstantial evidence indicated that elevated environmental temperatures had contributed to the

deaths. Forty-eight (48) of the 85 heat-related deaths occurred within the city limits; the remainder

occurred elsewhere in the county. Victims ranged in age from 24 to 88 years. At least 12 of the victims

were known to be taking psychotropic (mind-altering) drugs which may impair thermoregulatory function

or inhibit perspiration and increase a person’s susceptibility to heat-related illness or death. At least two

deaths occurred in group homes for the mentally ill, raising questions regarding the regulation and

licensure of such accommodations. Emergency rooms were reported to have been very busy, and some

had to be closed for a period of time during the heat wave because they were full to capacity. However,

use of a computer system allowed emergency medical system managers to adjust to the closure of

specific emergency departments.

Finding: One of the difficulties with measuring the mortality associated with a heat emergency is

the lack of definition for a heat-related death that is both standardized and practical. A standard

definition for heat-related death, such as the one used in Chicago, should be developed and adopted

for national use by all medical examiners.

Finding: The awareness of heat-related deaths by local medical examiners in Chicago and

Milwaukee in 1995 led to the initial recognition in those cities of excess deaths during heat-wave

periods.

Finding: In Chicago and Milwaukee, the people most affected by the heat were the elderly.

Recommendation: Since the elderly in urban areas are in the greatest danger during heat waves,

the NWS must proactively focus heat preparedness efforts toward this group.

Finding: Heat waves are not clearly recognized as public health emergencies.

Recommendation: Emergency response organizations at the Federal, state, and local levels should

be encouraged to recognize severe heat waves as potential natural disasters, and areas at risk

should be prompted to develop emergency response plans for severe heat waves. These plans

should target the groups most often affected by the heat, including elderly persons, particularly

those living alone; persons with chronic medical conditions, especially cardiovascular or

pulmonary disease; and persons taking psychotropic medications.

Recommendation: The analysis of morbidity during the July 1995 heat wave in Chicago and

Milwaukee should be investigated by public health officials in order to provide useful public health

information about the relationship of morbidity to mortality.
27

The vulnerability of the elderly in urban core areas was underestimated. Although it is known that the

elderly are more susceptible to heat-related illness because of their decreased physical ability to adapt to

extreme changes in environmental temperature, information collected for this assessment suggests that,

for some elderly in the urban core, there were additional social and behavioral factors which further

increased their vulnerability. Specifically, it was found that those most likely to be affected were those

who were: (1) unlikely to receive warnings and forecasts disseminated in the normal fashion; (2) unable

to fully appreciate the significance of the warnings and forecasts; (3) uninformed about proper

precautions and actions that they should take to protect themselves from the effects of the heat; (4) too

poor to have adequate air conditioning or to operate it even if available; (5) too frightened of crime to

leave their windows opened; (6) or too weak, infirm, or frightened to seek public shelter. Most

fundamentally, those at risk were isolated and lacked a concerned network of family and friends and, as a

last resort, attention from social agencies.

Finding: The vulnerability of the elderly in urban core areas was underestimated during the heat

wave.

Recommendation: Forecasters should target Heat Warnings, Watches, Advisories, and Statements

to those groups that are most vulnerable.
28
29

CHAPTER 3

PROVISION OF NWS

PRODUCTS AND SERVICES

Since the mid-July heat wave brought unprecedented conditions to Chicago and Milwaukee, this chapter

will focus on the products and services provided by the NWS Forecast Offices at Chicago, Illinois, and

Milwaukee, Wisconsin. The review criteria for NWS products, services, and actions are described in

appendix A.

 Chicago, Illinois

Forecasters at the Chicago NWS Forecast Office provided forecasts of state of the art accuracy as much

as 5 days in advance of the excessive heat. This information clearly conveyed important details

concerning excessive temperatures and high humidities but understated the severity of what would prove

to be a record event. A Heat Advisory was in effect prior to and throughout the event. As the event

neared, forecasters issued follow-up statements that relayed both emergency and climatological

information to the community. However, neither the Chicago forecasters nor local officials recognized

the potential for significant loss of life.

Extended Forecast Review

Information on expected weather conditions, generally greater than 48 hours in advance of the event, was

communicated through the NWS Extended Forecast Product. The extended forecast products issued by

forecasters at the Chicago NWS Forecast Office clearly called for hot, as well as humid, conditions well

in advance (as early as July 7). In fact, forecasters focused on humid conditions—an often difficult task

this far in advance.

Finding: The Extended Forecast Product issued by forecasters at the Chicago NWS Forecast

Office communicated the likelihood of high levels of heat and humidity 48 hours prior to the event.

Finding: Extended range forecasts of temperatures were generally within 3 to 5 degrees for high

temperatures and 5 to 7 degrees for low temperatures.

Forecast Review

Forty-eight hours prior to the event, emphasis focuses on the provision of accurate forecasts of weather

conditions and the communication of potential public hazards relating to the anticipated heat. In

addition, the Weather Service Operations Manual (WSOM) Chapter C-44, Non-Precipitation Weather

Hazards, allows for the issuance of an Outlook or Watch for excessive heat to provide early planning

information for both key officials as well as the general community. However, a Heat Outlook or Heat

Watch was not issued.
30

NWS forecasters at Chicago issued accurate and timely forecasts relating to the anticipated heat and

humidity. High temperature forecasts during this time frame were accurate to within 3 degrees. Low

temperature forecasts were accurate to within 6 degrees. The forecasts included descriptive wording that

added extra detail to the forecasts. Nonetheless, these forecasts understated the conditions that actually

occurred and forecasters (as well as local officials) were not aware of the impact these conditions would

have on the general public.

Finding: NWS forecasters at the Chicago Forecast Office communicated a forecast calling for

high heat and humidities 36 to 48 hours prior to the event.

Finding: Short-range temperature forecasts had state of the art accuracy. High temperature

forecasts were accurate to within 3 degrees. Low temperature forecasts were accurate to within 6

degrees. Both were underestimates.

Finding: Forecasters used descriptive terminology, such as "muggy" and "humid," to

communicate important weather information.

Finding: A Heat Outlook or Heat Watch was not issued as allowed for in WSOM Chapter C-44,

Non-Precipitation Weather Hazards.

Recommendation: The NWS should ensure that forecasters at all field offices understand the

flexibility provided by WSOM Chapter C-44 to issue a variety of critical information products on

heat-related issues.

Short Term Forecast Review

During the event, forecasters are expected to issue accurate meteorological, climatological, and safety

information on a frequent basis. Short-range temperature forecasts for Chicago were highly accurate. 

High temperature forecasts were accurate to within 2 degrees. Low temperature forecasts were accurate

to within 4 degrees. A Heat Advisory was issued for the city of Chicago 12 hours or more in advance of

the worst physical conditions and most heat-related deaths. Numerous statements were issued to inform

the community on the climatological aspects of the event. Fewer statements were issued, detailing safety

aspects and specific call to action information.

The wording of several forecasts was excellent. In particular, the Zone Forecasts issued at 4 a.m.,

Central Daylight Time (CDT), July 13, contained enhanced heat caution wording as well as specific

forecast heat index levels. For example, the headline highlighted "HEAT ADVISORY TODAY FOR A

HEAT INDEX OF 110 TO 120," and the forecast called for "OPPRESSIVE HEAT AND HUMIDITY."

Heat Advisories were issued daily. The first advisory was issued at 3:30 p.m., CDT, July 12, with

subsequent advisories issued at 4:15 a.m., CDT, July 13, and 5:15 a.m., CDT, July 14. Two excellent

statements were issued at 4:15 a.m., CDT, July 13, and 5:15 a.m., CDT, July 14, which contained both

accurate forecasts as well as call to action information.
31

Enhancement Concept 1: Stress the dangerous nature of excessive heat in

Finding: NWS forecasters at the Chicago Forecast Office issued accurate Short Term Forecasts

that included temperature, humidity, and heat index levels.

Finding: Heat Advisories were issued prior to and during the excessive heat event.

Finding: The initial Heat Advisory issued at 3:30 p.m., CDT, July 12, was issued under an

incorrect product title (Public Information Statement). A Non-Precipitation Weather Warning

should have been issued.

The Short Term Forecast, routinely issued every 3 or 4 hours, was the primary product issued to

distribute specific heat-related weather information and to follow up on previously issued Heat

Advisories. These forecasts contained little, if any, information relating to the potential impact of

anticipated weather conditions or call to action safety guidelines. The only attempt to target groups at

risk was in the daily Heat Advisory issuance.

Finding: NWS-issued forecast products contained highly detailed and accurate meteorological

information, including the heat index, but lacked call to action statements. Heat Advisories were

the only products that contained information relating to the potential impact of anticipated

weather conditions or call to action information.

Recommendation: Forecasters should focus on the health hazards associated with heat in

warnings, watches, forecasts, advisories, and statements. All products should include call to action

statements.

Recommendation: MICs and WCMs at all NWS forecast offices should work with state, city, and

local health officials to determine threshold values for dangerous heat index levels tailored to their

area.

Potential For Enhanced Service

Although the excessive heat was well forecast by forecasters at the NWS Forecast Office at Chicago,

there are several ways in which service to the public could have been enhanced.

With forecast or actual temperatures near 100EF, dew points near 80EF, and heat index levels above

110EF, the seriousness of these weather conditions could have been stressed in Warnings, Watches,

Advisories, and Statements.
32

Enhancement Concept 2: Keep a pulse on the community.

Enhancement Concept 3: Understand local problems of the community.

Enhancement Concept 4: Develop local studies for the community.

Enhancement Concept 5: Keep the community well informed.

Enhancement Concept 6: Work with commercial service providers.

It was nearly impossible for forecasters to learn of the increasing heat-related deaths until after the peak

period of temperature. The earliest indication of a developing crisis was an enormous increase in

emergency room admissions. At one point, 18 Chicago-area hospitals were in bypass or unable to admit

more people into the emergency room. This occurred relatively early in the event. During times of

excessive heat, forecasters should establish contact with public health officials to obtain this information.

Early indications suggest that the elderly in urban areas were vulnerable to the excessive heat. 

Forecasters should issue targeted products addressed to the most vulnerable.

In some cases, there are thresholds of temperature, humidity, and hence heat index at which heat-related

problems increase. Local studies, in cooperation with health officials, could better define these critical

values. They will most likely vary from region to region and, perhaps, city to city.

Once forecasters target specific groups and critical threshold heat values, keep the community informed

via frequent statements.

Work with commercial service providers to develop a heat hazards training element for their radio and

television customers to improve the on-air delivery of forecast information to the public.

Post-event Coordination

The MIC and WCM at the Chicago NWS Forecast Office have been closely involved with state, city, and

local health and emergency management officials since the July heat wave and are members of the

Mayor’s Commission on Extreme Weather Conditions. As a result, significant progress has been made

towards improvement of weather warning and forecast services to the community during extreme

weather events, including heat.
33

 Milwaukee, Wisconsin

Forecasters at the Milwaukee NWS Forecast Office provided accurate and timely forecast information as

much as 5 days in advance of the excessive heat. This information clearly conveyed important details

regarding excessive temperatures and high humidities. A Heat Advisory was in effect prior to and

throughout the event. As the event neared, forecasters frequently issued a variety of well-written

statements that relayed emergency and safety information to the community. However, neither

Milwaukee forecasters nor local officials recognized the significant potential for loss of life.

Milwaukee NWS forecasters exceeded operational requirements in keeping the community informed. 

Heat Advisories were issued for a consecutive 2-day period. This action, based on sound professional

judgment, conveyed important information on the anticipated duration of the event. Additionally, an

Outlook indicated the likelihood of 100EF temperatures over 40 hours in advance.

Extended Forecast Review

Information on expected weather conditions, generally greater than 48 hours in advance of the event, was

communicated through the NWS Extended Forecast Product. The Extended Forecast Products issued by

forecasters at the Milwaukee NWS Forecast Office clearly called for hot conditions well in advance (as

early as July 8). Extended forecasts did not emphasize humid conditions. Demonstrating extra initiative,

NWS forecasters at Milwaukee issued two Special Weather Statements, indicating the likelihood of

dangerous heat. Special Weather Statements issued at 3:45 p.m., CDT, July 11, and 5:15 a.m., CDT, July

12, were timely and accurate. Both contained information targeting the elderly (for example, "the

elderly, very young, and persons with heart problems are most at risk in extreme heat"). These

statements, issued 40 hours prior to the event, provided the community advance notice of the expected

heat and raised awareness of physiological risk.

Finding: The Extended Forecast Product issued by forecasters at the Milwaukee NWS Forecast

Office clearly communicated the likelihood of unusually high levels of heat 5 days prior to the

event.

Finding: Extended range forecasts of temperatures were initially 6 to 10 degrees low in the 3- to

5-day range but improved to within 2 degrees in the 1- to 2-day range.

Finding: Two Special Weather Statements were issued 40 hours prior to the event and contained

call to action information for the elderly and others at risk.

Forecast Review

Forty-eight hours prior to the event, emphasis focuses on the provision of accurate forecasts of weather

conditions and the communication of potential public hazards relating to the anticipated heat. In an

aggressive maneuver, the Milwaukee NWS forecasters issued a Heat Advisory for 2 consecutive days. 

This action provided local officials with excellent planning information. Forecasts were accurate, timely,

and focused on the anticipated heat and humidity. Temperature forecasts during this time frame were

accurate to within 2 or 3 degrees. The quality of forecasts was high, with forecasters including

descriptive wording that added extra detail to the forecasts. Nonetheless, similar to Chicago, forecasters

(as well as local officials) did not appreciate clearly the impact these conditions could and did have.
34

Finding: NWS forecasters at the Milwaukee Forecast Office clearly, effectively, and accurately

communicated a forecast calling for high heat and humidities 36 to 48 hours prior to the event.

Finding: Short-range temperature forecasts were accurate. Initial errors in forecast accuracy

improved to within 2 or 3 degrees at least 24 hours prior to the onset of the heat wave.

Finding: Forecasters used descriptive terminology, such as "muggy" and "humid," to

communicate important weather information.

Finding: A Heat Advisory was issued for 2 consecutive days, providing local officials excellent

planning information.

Short Term Forecast Review

During the event, forecasters are expected to issue accurate meteorological, climatological, and safety

information on a frequent basis. Short-range temperature forecasts for Milwaukee were highly accurate. 

Temperature forecasts were accurate to within 0 to 3 degrees. NWS forecasters at Milwaukee took an

integrated, multi-tier approach to informing the community of the impending dangerous heat. Heat wave

safety rules were disseminated as early as July 13 in warnings, forecasts, and statements. A Heat

Advisory was issued for the city of Milwaukee 12 hours or more in advance of most heat-related deaths. 

Additional Heat Advisories were issued twice daily in conjunction with the early morning and late

afternoon forecasts. Specifically, advisories were issued at 12:35 p.m., CDT, July 12; 5:15 a.m., CDT,

July 13; 3:35 p.m., CDT, July 13; 4:25 p.m., CDT, July 14; 3:30 p.m., CDT, July 14; and 4:20 a.m., CDT,

July 15. All advisories contained detailed temperature, humidity, and heat index information in addition

to call to action statements for the elderly, the very young, and the infirm.

Finding: NWS forecasters at the Milwaukee Forecast Office issued accurate Short Term

Forecasts that included temperature, humidity, and heat index levels.

Finding: Heat Advisories were issued prior to and during the excessive heat event.

Finding: Heat index levels were provided in the first period (first 6 hours) of the Zone Forecasts.

NWS forecasters at Milwaukee used a combination of Short Term Forecasts, Heat Advisories, Special

Weather Statements, and one Severe Weather Statement to convey urgent excessive heat information. 

All Short Term Forecasts contained public safety information. Heat Advisories were issued at 4 a.m. and 
35

Enhancement Concept 1: Focus on the highest at-risk groups.

Enhancement Concept 2: Keep a pulse on the community.

4 p.m., CDT, with follow-up special weather statements issued at 10 a.m. and 10 p.m., CDT. These

issuances provided a continuum of information to the community. Several statements targeted high risk

groups, such as the elderly, the very young, and the infirm. However, there was minimal targeting of

specific areas at risk, such as the urban core. Numerous climatological information statements were also

issued.

Finding: NWS-issued forecast products contained highly detailed and accurate meteorological

information, including the heat index.

Finding: NWS forecasters at the Milwaukee Forecast Office issued frequent Heat Advisories and

Special Weather Statements to keep the community well informed.

Finding: All warnings, forecasts, advisories, and statements were of high quality and contained

accurate forecast details, including heat index levels.

Recommendation: MICs and WCMs at all NWS forecast offices should work with state, city, and

local health officials to determine threshold values for dangerous heat index levels tailored to their

area.

Potential For Enhanced Service

Although forecasters at the NWS Forecast Office at Milwaukee kept the community well informed on the

heat wave, there are a few ways in which service could have been enhanced.

Large urban areas pose unique problems during excessive heat situations. Forecasters are encouraged to

provide frequent statements targeted to the groups at higher risk; in this case, the elderly and infirm

residing in urban areas.

It was nearly impossible for forecasters to learn of the increasing heat-related deaths until after the peak

period of temperature. The earliest indication of a developing crisis was an enormous increase in

emergency room admissions. At one point, several Milwaukee-area hospitals were in bypass or unable to

admit more people into the emergency room. This occurred relatively early in the event. During times of

excessive heat, forecasters should establish contact with public health officials to obtain this information.
36

Enhancement Concept 3: Develop local studies for the community.

Enhancement Concept 4: Work with commercial service providers.

In some cases, there are thresholds of temperature, humidity, and heat index at which heat-related

problems are increased. Local studies, in cooperation with health officials, could better define these

critical values.

Work with commercial service providers to develop a heat hazards training element for their radio and

television customers to improve the on-air delivery of forecast information to the public.

Post-event Coordination

Since the July heat wave, the MIC and WCM at the Milwaukee NWS Forecast Office have been closely

involved in coordinating emergency preparedness plans with local officials for extreme heat events.
37

CHAPTER 4

COMMUNICATION, EMERGENCY PREPAREDNESS,

AND COMMUNITY RESPONSE

"We knew it was going to be hot...but we had no idea it could be that deadly."

Local Emergency Official

Extreme heat may be the most underrated and least understood of the deadly weather phenomena. The

communities of Chicago and Milwaukee had in place extensive disaster preparedness plans and response

procedures for many weather and flood hazards. However, as seen in the July heat wave, extreme heat

was not one of the disasters they were prepared to respond to effectively. Local officials clearly did not

understand the connection between very high heat and humidity and high death rates. In fact, the exact

definition of heat-related deaths and illnesses and the extent of the mortality and morbidity associated

with extreme heat is a debated topic in the medical, forensic, and public health communities.

The effects of a heat wave are often delayed in terms of: (1) increased illness and mortality and (2) the

detection of these increases by the medical, public health, and public safety monitoring systems in

communities. Heat is not like a flood, hurricane, or tornado that is a visible phenomenon which

dramatically impacts a community, leaving identifiable victims who receive immediate emergency

medical treatment.

In both Chicago and Milwaukee, extreme heat was viewed as a public health concern, not as a major

community emergency or disaster. Therefore, this event fell within the purview of the local health

department to provide planning for and coordinate community response to these events. Heat waves

were outside the realm of local disaster or emergency operations plans of the emergency management

officials and the traditional disaster response systems. This shaped the nature and extent of each

community’s actions during the July heat wave.

To better understand how local officials prepared for and responded to this event, the communication,

emergency preparedness, and community response actions will be reviewed for Chicago and Milwaukee

based on interviews with local health and emergency response officials. The media response to this

event will also be discussed in terms of how they provided the public with: (1) NWS warnings,

forecasts, advisories, and statements; (2) the risks of excessive heat; and (3) safety tips.

In general, the warning process involves a series of interdependent actions in order to achieve its

goal—to maximize the number of people who take timely and appropriate protective action. This

warning process may be viewed as an integrated warning system comprised of three functional

components: (1) scientific detection and prediction; (2) emergency response, including warning; and (3)

correct protective public response.
38

If any one of these components fails, the entire system can fail. The first component has been reviewed

in preceding chapters; we focus here on factors affecting the second and third components.

Communication

The communication process involves two steps: (1) the communication of critical weather information

by the NWS to emergency managers, the news media, and other agencies that are part of the public

warning process; and (2) the communication of this information via emergency preparedness

organizations and the media to those affected. The goal of effective communication is to maximize the

number of people who take timely and appropriate protective action.

In the case of the July 1995 heat wave, it appears that the first step of this process went satisfactorily at

both Chicago and Milwaukee. Unlike small, highly-localized, short-lived but violent phenomena, such as

tornadoes, the nature of a heat wave—its broad extent, gradual development, and slow subsequent

motion—was such that it was forecast accurately days in advance. Thus, the performance of rapid

response communications links (such as NOAA Weather Radio [NWR], NOAA Weather Wire Service

[NWWS], and the Emergency Broadcast System) was not an issue here.

Despite timely NWS warnings, forecasts, advisories, statements, and effective media coverage of the

event, the communication process failed in Chicago and Milwaukee during the second step. There was a

failure by city officials to translate the physical character of the heat wave (maximum temperatures,

minimum temperatures, humidities, spatial extent, and duration) into human impacts. Emergency

preparedness for Chicago and Milwaukee will be reviewed in the next section.

Finding: Despite timely NWS warnings, forecasts, advisories, statements, and effective media

coverage of the event, city officials had neither the experience nor emergency response capabilities

to translate the physical characteristics of the heat wave into human impact.

Recommendation: NWS offices should work with local officials to develop a public awareness and

community response plan for such events, especially among vulnerable or disadvantaged groups.

Media Coverage

The July 1995 heat wave was a unique meteorological event for the Chicago and Milwaukee media. 

While the electronic (radio and television) and print media provided heat-wave forecasts and healthrelated reports, they failed to foresee the number of deaths that would result from this unprecedented

weather event. Media representatives interviewed in Chicago and Milwaukee reported good working

relationships with their respective NWS offices and were satisfied with the level of service provided.

The Chicago and Milwaukee media received weather information from both the NWS and a variety of

commercial weather vendors. Staff meteorologists at radio and television stations gave the NWS high 
39

marks for timely and accurate forecasts and related services during the heat wave. They found NWS

forecasts to be consistent with their own. According to Chicago’s WGN-TV meteorologist Tom Skilling,

"The NWS made it absolutely clear that this extremely hot air mass was coming our way."

Radio and television stations provided the public with weather-related information through two different

venues: weather and news reporting. While media coverage reported dangerous heat levels and offered

tips on staying cool, no one anticipated the number of deaths that would accompany the event. An article

in the Milwaukee Journal Sentinel (July 25, 1995) noted, "Milwaukee’s TV weathercasters did their job

well in letting us know that killer heat was on its way. What viewers did with that information helped

determine how well they coped with the heat." 

Several media representatives noted that people understand watch/warning terminology for

thunderstorms and winter storms but not for heat. A few voiced concerns about the heat index. For

others, triple digit temperatures, not the heat index, made the weather the top story. All said they

reflected severity of the event in their terminology and in changes of story context from "uncomfortable

heat" to "dangerous heat."

Finding: Media coverage of the July 1995 heat wave in Chicago and Milwaukee was substantial

from both meteorological and health angles.

Finding: Staff meteorologists at radio and television stations gave the NWS high marks for timely

and accurate forecasts and related services during the heat wave.

Finding: The Chicago and Milwaukee media have not developed a public response to heat

hazards as they have for other severe weather phenomena.

Recommendation: The NWS must enhance its public education campaign regarding the use of the

heat index and the dangers of heat. The media and the private sector should be enlisted as

partners through professional associations, such as the American Meteorological Society and the

National Weather Association.

 Chicago, Illinois

Emergency Preparedness

Chicago’s disaster preparedness planning responsibility rests in the Chicago Fire Department. Their

Office of Emergency Management maintains the city’s emergency operations plan. It addresses the major

disasters believed to threaten Chicago. A disaster is an event that causes community impacts which

outstrip any single agency’s ability to respond and meet the demands for help or resources. Extreme

temperatures were not identified as one of the hazards that could cause a disaster in Chicago; a heat wave

was viewed as a health emergency. An emergency is defined as heavily taxing the response capabilities

of an agency or governmental function, such as emergency medical services, fire suppression, or crowd

control. Hot weather, considered a health emergency, falls under the responsibility of the Chicago

Department of Health. Therefore, the city’s response to extremely hot temperatures is not addressed in

the citywide disaster preparedness process.
40

The Chicago Health Department’s plan for heat waves that was in effect July 14 and 15 had three basic

components. First, public service announcements on heat safety actions are sent to the media outlets in

early June as a general preparedness measure for the coming summer. Second, forecasts for excessive

heat are brought to the attention of the media news departments by the health department. These are

monitored through weather forecasts on radio and television. Third, the Department of Human Services,

the Department of Aging, and the Chicago Police Department are notified by the Department of Health of

heat wave forecasts. When excessive heat is forecast, cooling centers are activated to provide service to

the elderly at community centers. 

Additionally, individual city agencies have internal heat wave response plans. These include such

actions as relief for firefighters battling blazes, precautions for public works and sanitation crews

working outdoors in the heat, police awareness to heat-related problems, and spraying water on metal

bridges to prevent buckling. The city also has in place a medical emergency plan, covering both patient

transport and hospital response to mass casualty incidents. This plan is designed to provide a

coordinated delivery of medical services in case of a disaster that would overload hospitals with victims. 

The goal is to simultaneously activate the area hospitals’ individual disaster plans and coordinate patient

transport to hospitals based on patient need and available medical resources.

Chicago has a long history of meteorological forecast support from the private sector. This has

traditionally focused around winter weather and city snow removal operations. The Chicago Department

of Streets and Sanitation, Bureau of Street Operations, serves as the focal point for all weather forecasts

and information for the city. Their dispatch center is staffed around the clock, 7 days a week. The city

contracts for meteorological support from three different companies. They receive, via telephone

facsimile, forecasts three times daily from Murray and Trettel, Incorporated. This firm also issues its

own storm warnings for severe summer weather and snow and ice storms and sends them to the Bureau

of Street Operations. The storm warnings are faxed out by Street Operations to most city agencies. The

dispatchers do not know the differences or similarities between these private storm warnings and NWS

warnings. Chicago also purchased a series of street surface sensors and meteorological support services

from Surface Systems Incorporated (SSI). This firm provides real-time access to the sensors in the city

and surrounding area. They also provide computer access to NWS forecast products that can be printed

and NWS Doppler weather surveillance radar products through a Next Generation Radar Information

Dissemination Service vendor. The dispatchers must actively retrieve weather information, warnings,

watches, and forecasts on this computer system. The third company the city uses is Compu-Weather, and

it receives forecasts twice daily from this firm.

Chicago receives NWS warnings, watches, and forecasts indirectly via The Weather Channel, which is

constantly monitored in the dispatch center and over the SSI weather computer. There was no direct link

to the Chicago NWS Forecast Office. The dispatch center does not subscribe to the NWWS nor does it

monitor NWR.
41

Finding: At the time of the July 1995 heat wave, the emergency preparedness program for

extreme heat in Chicago was organized and administered from the public health department,

which was different from other hazardous weather events.

Finding: Officials in Chicago did not realize the difference between NWS weather warnings and

private sector warnings.

Recommendation: The Chicago NWS Forecast Office should work with Chicago 

officials to provide user training on NWS watch/warning products.

Community Response

Chicago officials were aware that the forecast was for hot weather July 13 and 14, but they did not fully

understand the meaning of the heat index forecast nor did the forecast clearly convey the true severity of

what would occur. Moreover, they could not anticipate the potentially catastrophic nature of such an

extreme heat wave and the extent of the threat to public health. It was beyond anyone’s realm of

experience. Officials indicated that even if warnings for excessive heat had been issued by the Chicago

NWS Forecast Office, they would not have changed their response. Community centers stayed open as

cooling facilities for the elderly but appeared to have been only slightly used. Public service

announcements were sent out about the cooling centers. Individual city agencies activated their heat

response operating procedures, stressing the safety of their personnel. The city prepared for several days

of very uncomfortable weather that would affect city service operations. Weather forecasts for extreme

heat were received in the Bureau of Street Operations dispatch center. However, there was no city

protocol for relaying Warnings, Watches, Forecasts, Advisories, and Statements to other city agencies. 

The heat wave was not identified as a major weather or public health threat. Therefore, the Chicago

Department of Health relied on media-relayed NWS forecasts and periodic NWS briefings via telephone.

The real-time tracking of increased demand for emergency medical services did not detect the increased

hospital load during the heat wave. Therefore, the city’s medical emergency plan was not activated. 

Individual hospitals did implement their individual patient overload response plans, which called for

ambulances with patients to bypass emergency rooms that were full. The patients were taken to less

crowded hospitals. The transportation and treatment of patients suffering heat-related illnesses was not

coordinated citywide.

The first indication of the catastrophic impact of the heat wave was the arrival of large numbers of

victims at the Chicago Medical Examiner’s Office. The true nature of the disaster revealed itself as more

and more victims were discovered in their homes. In many ways, this was a silent disaster, quietly killing

hundreds of people who did not escape the deadly heat. When it was all over, Chicago had experienced

its worst weather-related disaster with 465 heat-related deaths that occurred from July 11-27.
42

Recovery

Immediately after the impact of the heat wave was recognized, Chicago officials began a new program of

short-term actions for a citywide heat response program. These included an interim Heat Emergency

Plan and a proactive city response to heat waves. A Mayoral Commission on Extreme Weather

Conditions was convened, with the task of recommending long-term plans for preparing for and

responding to heat waves and other weather hazards.

In parallel with the Commission, officials at the Chicago Department of Health began immediately after

the event to develop a detailed interim Heat Emergency Plan and a proactive city response to heat waves. 

This included daily monitoring of private sector and NWS forecasts by health officials. The city has

directed Murray and Trettel, Incorporated, to provide a 5-day forecast for the heat index based on the

NWS computational formula. These daily forecasts are faxed to the Chicago Department of Health and

other city agencies. The Chicago Department of Health also developed a Heat Emergency Plan which

calls for the health department to issue Heat Alert, Heat Warning, and Heat Emergency messages to the

public based on NWS forecasts of heat index temperatures. Many agencies have stepped up their

surveillance of those citizens at risk from heat-related illness and death. The Heat Emergency Plan also

establishes a city command post and phone bank if heat index temperatures exceed 105EF.

The Commission was created to advise the Mayor of Chicago on proposals for dealing with all types of

hazardous weather that affect Chicago. Its mission is to document the past occurrence and future risk of

hazardous weather conditions and develop emergency response capability as part of the city’s emergency

planning. Members for all city agencies are appointed to the Commission as is the MIC from the

Chicago NWS Forecast Office. The Commission is divided into six committees: weather, mortality and

morbidity, geriatric behavior, role of the government, role of the private sector, and public education and

outreach. Members of the Commission have talked with representatives from both Philadelphia,

Pennsylvania, and St. Louis, Missouri, to study their community heat response plans and operations. 

Chicago officials have identified these two cities as having effective community heat response programs.

 Milwaukee, Wisconsin

Emergency Preparedness

The emergency management structure for Milwaukee is located in the Milwaukee County Division of

Emergency Government. Local emergency management is well organized, has a very good relationship

with the Milwaukee NWS office, and generally appears to be quite responsive to weather emergencies. 

However, local decision-makers do not receive weather information directly from the NWS via the

NWWS or NWR. For routine weather information, local officials rely solely on the media. Local

emergency officials receive emergency weather information for tornadoes, severe thunderstorms, and

flash flooding via the Wisconsin Criminal Justice Information System (WCJIS), which has a fullyautomated interface with NWWS to disseminate warnings and watches to all local law enforcement

agencies. Printed warnings and watches are received by local officials. Other critical information (heat

waves, winter weather, etc.) is not relayed by WCJIS.
43

The city of Milwaukee’s heat wave preparedness and response is coordinated by the Milwaukee Health

Department. Several years ago, they brought together the Hot Weather Task Force, representing various

public and private organizations, to develop a coordinated response plan to extreme and prolonged high

temperatures. The plan calls for the issuance of Heat Warnings and Heat Alerts based on a forecast of

hot weather for 2 or more consecutive days. These issuances, designed to alert the media, public, and

other response agencies, include information on air-conditioned public facilities, cool spots (i.e.,

libraries), pools, cooling centers, and senior centers that are open. They also include phone numbers for

various agencies, providing health advice during heat waves and specific health facts and tips. These

issuances are disseminated to the media independent of NWS products.

Community Response

In Milwaukee, the community response to the heat wave was similar to that of Chicago. Local officials

expected the predicted July heat wave to involve very hot weather and oppressive humidity with some

health risks for the elderly. The event was not viewed as extremely dangerous and potentially deadly.

On July 11, the Milwaukee Department of Health issued a Hot Weather Advisory for the impending heat

wave. The advisory was based on NWS forecasts for high temperatures and humidity. Lists of airconditioned cooling centers at community centers, public facilities, and libraries were in the advisory. 

The heat information telephone lines were staffed from July 12 to 14 to answer health-related questions

from the public. The city advisory was forwarded to area health facilities and the media. Agencies that

were part of the Milwaukee Department of Health Heat Disaster Plan were notified of the advisory. 

There was a sense of informal cooperation among the agencies but no formal coordination of efforts.

The magnitude of the problem only became apparent when health officials noticed the increase in heatrelated morbidity and mortality. The city activated its Emergency Medical Services response plan, and

individual hospitals activated their disaster plans. The scope of the disaster was not fully realized until

the death toll rapidly rose. The city opened more shelter space to help residents escape the deadly heat. 

The Milwaukee Division of Emergency Government became aware of the disaster when they received a

request for cots for the cooling shelters. Once again, the silent killer of extreme heat had struck before

the danger had been fully recognized by local officials. In Milwaukee, 85 heat-related deaths were

recorded from July 14-17, 1995.

On July 14, the Milwaukee Department of Health, using its own criteria (3 consecutive days with heat

indexes above 95EF), issued a health warning. It is not clear if or how the warning was perceived

differently from the NWS Heat Advisory by the media and the public. According to health department

officials, there was at most minimal confusion resulting from having warning messages from different

sources using different wording. They believe that the messages, rather than conflicting with each other,

served to emphasize the heat concern in the public’s consciousness. Activities that were in operation

prior to or soon after the start of the heat wave included a fan distribution program, the operation of

cooling centers, and contacting of shut-ins.
44

Recovery

In Milwaukee, a Community Task Force on Summer Weather Emergencies was convened immediately

after the heat wave. The Task Force consists of participants from the NWS; state, county, and city

divisions of emergency government and public health; emergency medical groups; utilities; volunteer

organizations (Salvation Army, American Red Cross, etc.); and the media. The Task Force is

investigating improvements in preparedness and response to summer weather hazards.

Finding: Chicago and Milwaukee officials and the public did not fully understand the heat index

or the extent of the threat from heat waves.

Recommendation: The NWS must enhance its community education campaign regarding the use

of the heat index and the dangers of heat.
45

CHAPTER 5

CASE STUDIES IN

HEAT WAVE PREPAREDNESS

In addition to Chicago and Milwaukee, the NOAA Disaster Survey Team visited Philadelphia,

Pennsylvania, and St. Louis, Missouri. These cities experienced deadly heat waves in 1993 and 1980,

respectively. The Survey Team wanted to determine whether previous experience during heat

emergencies affected the impact of the July 1995 heat wave in these two cities.

Recommendation: NOAA should actively encourage other Federal agencies, such as the

Department of Health and Human Services, the Environmental Protection Agency, and the

Federal Emergency Management Agency, to join in research on excessive heat, mortality, and

morbidity.

Recommendation: The NOAA Chief Scientist should convene a workshop comprised of

interagency physical scientists, private sector providers, social scientists, and epidemiologists to

provide operational research recommendations in light of the scientific advances made over the

last decade. The relationship between heat-related mortality and the heat index, as well as other

proposed predictors of heat stress, should be simultaneously evaluated to determine which method

most accurately predicts the health consequences of a heat wave.

 Philadelphia, Pennsylvania

During a 3-week period in July 1993, the Philadelphia County Medical Examiner reported approximately

118 heat-related deaths (CDC, 1994; CDC, 1993). Although the medical examiner was initially criticized

for overestimating the number of deaths, a subsequent evaluation by CDC investigators confirmed the

findings. In fact, it was found that similar increases in deaths during the heat wave had occurred in other

urban areas near Philadelphia although they had not been recognized at the time.

From July 12 through August 17, 1995, 72 deaths in Philadelphia were attributed to the heat. Forty-two

(42) of these occurred between July 13-21 when the same heat that had affected Chicago and Milwaukee

blanketed Philadelphia. Of the 72 deaths, 54 (75 percent) occurred in persons over 60 years of age. 

Many of the deceased had pre-existing medical conditions which may have made them, for physiologic

or behavioral reasons, more susceptible to the effects of the heat.

As a result of its experience during the 1993 heat wave, the city of Philadelphia established a Heat Wave

Preparedness Task Force which developed an extensive and detailed Heat Response Emergency Plan for

reacting to heat emergencies. The Plan provides a comprehensive system of prompt notification and 
46

mobilization of agencies during an excessive heat event. Participants in the heat Plan include not only

the Philadelphia Department of Health but also the Philadelphia Corporation on Aging, the Pennsylvania

Emergency Management Agency, the American Red Cross, representatives of the public utilities, and the

NWS. Year-round preparedness is emphasized, and participating groups meet throughout the year to

plan and coordinate their activities. The Heat Hotline, established during the 1993 heat wave, is the

backbone of the emergency response and is managed by the Philadelphia Corporation on Aging. In

response to calls received by the Hotline, teams consisting of a nurse and an environmental health

practitioner evaluate the residences of persons potentially at risk and assess the resident’s health and their

ability to cope with the heat. Other activities of the Heat Wave Preparedness Task Force include the

establishment of a plan for assisting the homeless during a heat emergency and modification of local

ordinances to require landlords of multiunit residences housing the elderly to maintain temperatures

below a certain threshold.

Philadelphia’s Heat Response Emergency Plan is activated by Heat Warnings issued by the NWS. 

Emergency activities are mobilized on the basis of a coordinated prediction plan between the NWS and

the University of Delaware. The University of Delaware uses an alternative model developed by

Professor Laurence Kalkstein, Center for Climatic Research, University of Delaware, and funded by the

Environmental Protection Agency (Kalkstein and Smoyer, 1993; Kalkstein, 1993; Kalkstein, 1991;

Kalkstein and Davis, 1989; Kalkstein and Valimont, 1986). The Kalkstein model first identifies

commonly occurring types of summer air masses. This is done through a statistically based classification

system which considers several weather forecast variables (air temperature, dew point temperature,

atmospheric pressure, cloud cover, wind speed, and direction) at four time points in each 24-hour period. 

For many cities, Kalkstein claims that one type of air mass is associated with the greatest increase in

mortality. For Philadelphia, this air mass is identified as maritime tropical, oppressive. However, not all

days within this air mass type are associated with elevated mortality totals. The model further identifies

which days within the high risk air mass will have elevated mortality. In Philadelphia, the factors that

contribute to high daily mortality when the high risk air mass is present include the number of

consecutive days within the air mass, the date in the season, and maximum temperature. Ironically, the

air mass described in chapter 1 that produced the severe conditions on July 14 and 15 in Philadelphia was

not maritime tropical.

In 1994, the NWS initiated a new Health Watch/Warning System in coordination with Pennsylvania

emergency management officials. In 1995, the city of Philadelphia started an enhanced Health

Watch/Warning System based on the Kalkstein model. The system consists of three levels: Health

Watch, Health Alert, and Health Warning. A Health Watch is issued by the Philadelphia Health

Commissioner 2 days prior to the forecasted arrival of a high risk air mass. A Health Alert is issued

1 day prior to the forecasted arrival of a high risk air mass. These issuances are coordinated with the

NWS Forecast Office at Mt. Holly, New Jersey. A Health Warning is issued by the Philadelphia Health

Commissioner either the afternoon before or the morning of the forecasted occurrence of a high risk air

mass. Depending on the number of excess deaths predicted by the model, one of three Health Warnings

is issued. A Level One warning is issued if one to four heat-related deaths are predicted; a Level Two

warning, if five to fourteen deaths are predicted; and a Level Three warning, if fifteen or more deaths are

predicted. The Health Warning is only issued in conjunction with the issuance of a Heat Warning by the

NWS. 
47

These Heat Warnings are based on heat index values reaching 105EF for 3 hours or more for 2

consecutive days.

Advocates of Kalkstein’s work believe that this model can better predict the true health risks associated

with a specific day than can the heat index criteria used by the NWS. This is because it models the

relationship between meteorological characteristics and mortality and takes into account the effect of

additional non-meteorological variables. There is not yet sufficient data to demonstrate clearly whether

in fact the Kalkstein method is consistently better at predicting the health effects of a heat wave. For

example, between July 12 and August 16, 1995, the Kalkstein model recommended the issuance

of Health Warnings on 15 days in Philadelphia. On nine of these days, the NWS also issued warnings. 

Of the 70 heat-related deaths that were recorded during that period, 17 (24 percent) occurred on days

when warnings were issued by the NWS and recommended by Professor Kalkstein; 15 (21 percent)

occurred on days when only Professor Kalkstein recommended a warning; 38 (54 percent) occurred on

days when no warnings were issued. The extent to which mortality was mitigated by appropriate

community response based on these warnings is also not known.

With the heightened awareness of city officials to the implications of high heat index values in

conjunction with a re-evaluation of Heat Advisory thresholds currently used by the NWS, the heat index,

with or without modification, may be as predictive as any proposed alternative models. Before being

adopted on a wide scale, any alternative method for predicting Heat Warnings needs to be thoroughly

evaluated. It is recommended that the relationship between heat-related mortality and the heat index, as

well as other proposed predictors of heat stress, should be simultaneously evaluated to determine which

method most accurately predicts the health consequences of a heat wave.

There has been significant research in the area of the health effects of extreme heat since the current

NWS heat index and warning/watch/advisory criteria was established. Many of the publications have

appeared since WSOM chapters were written. Research has been in the fields of public health,

epidemiology, climatology, meteorology, gerontology, sociology, and geography (Kilbourne, 1989;

Kalkstein, 1991; Lee, 1980; Riebsame, 1985; Riebsame, et al., 1986). This indicates the need for review

of current knowledge on the impact of heat to health and public safety as well as a review of NWS

operations.

Finding: Philadelphia’s Heat Wave Preparedness Task Force developed an extensive and detailed

plan for responding to heat emergencies.

Finding: Philadelphia’s Heat Response Emergency Plan is activated by Heat Warnings issued by

the NWS.

Finding: Emergency heat-related activities in Philadelphia are mobilized on the basis of

predictions of an alternative model developed by Professor Laurence Kalkstein, Center for

Climatic Research, University of Delaware.

Finding: It is not clear how much better the Kalkstein model compares with other models in

predicting the health effects of a heat wave.
48

Recommendation: The Kalkstein model should be reviewed after its proposed expansion to

Chicago, Illinois, and Atlanta, Georgia, in 1996.

The NOAA Disaster Survey Team believes the following recommendation to be of particular importance.

NWS Actions

During the July 1995 heat wave, forecasters at the NWS Forecast Office at Mt. Holly, New Jersey

(whose responsibility includes the Philadelphia metropolitan area), took aggressive actions to inform

their community of the dangerous heat wave. Accurate and timely forecast information was provided as

much as 5 days in advance of the excessive heat. Products issued by NWS forecasters clearly conveyed

important and accurate forecast information regarding excessive temperature and high humidities. 

A Heat Warning/Advisory was in effect throughout the event. In fact, Heat Warnings/Advisories were

issued for a consecutive 2-day period. This action, based on sound professional judgment, conveyed

important information on the anticipated duration of this event.

As the event neared, the office issued a variety of frequent, well-written statements that relayed

emergency and safety information to the community. Statements were often targeted to high risk groups

and areas. NWS forecasters exceeded operational requirements in keeping the community informed. An

Outlook product indicated the likelihood of dangerous heat over 48 hours in advance of highest

temperatures. In an unusual and highly successful move even prior to the issuance of a Heat Advisory,

Zone Forecasts were highlighted to reflect the anticipated dangerous heat. Temperature forecasts were

highly accurate and generally verified to within 2 or 3 degrees. NWS forecasters were also in contact

with state, city, and local officials during the event.

Finding: NWS forecasters clearly, effectively, aggressively, and accurately communicated a

forecast for the Philadelphia area calling for dangerously high heat and humidities 36 to 48 hours

prior to the event.

Finding: Recognizing the unique situation of an urban center, NWS forecasters issued a Heat

Warning for Philadelphia (the highest level possible) for a consecutive 2-day period. This action

provided community officials with key planning information.

Recommendation: NOAA should quantify the urban heat island effect to incorporate in NWS

Heat Warnings, Watches, Advisories, and Statements.

Media Coverage

Philadelphia summers are hot and humid, and the media are extremely knowledgeable about the dangers

of excessive heat. During the July 1995 heat wave, the citizens of Philadelphia received excellent and

thorough coverage of the event.
49

 St. Louis, Missouri

As in Philadelphia, most long-term residents of St. Louis have had personal experience with at least one

severe heat wave. The killer heat wave of 1980 claimed 113 lives (Kilbourne, et al., 1982; Jones, et al.,

1982). The number of deaths attributed to a 1966 heat wave was estimated to be as high as 400. Since

1981, Missouri has required that heat-related deaths or illnesses be reported to the State Health

Department. In 1981, the city of St. Louis established Operation Weather Survival, a loose affiliation of

agencies involved in responding to heat emergencies and coordinated by the local chapter of the United

Way.

During the summer of 1995, there were 27 heat-related deaths in St. Louis City and 4 in St. Louis

County. Of these 31 deaths, 22 occurred between July 14 and July 19. The victims ranged in age from

36 to 89 years.

Similar to Philadelphia’s Heat Wave Preparedness Task Force, Operation Weather Survival includes

outreach programs, an air conditioner distribution program, and the establishment of cooling centers

when required. Environmental health monitors visit addresses where heat deaths have occurred to

determine if there are additional people at risk. A computer-operated calling system was used for the

first time in 1995 to check on elderly residents.

Operation Weather Survival’s Heat Response Plan is activated by Heat Warnings issued jointly by the St.

Louis Department of Health and the St. Louis County Health Department rather than warnings issued by

the NWS. Although warnings issued by St. Louis City and County and the NWS often coincide, the

city’s Heat Warnings are based on readings of a wet bulb globe thermometer monitored by the St. Louis

Department of Health. The wet bulb globe thermometer, developed in 1957 to set limits to military

training during hot weather, gives a temperature which is adjusted to reflect heat loss/gain due to

evaporative and radiative mechanisms (Departments of the Army and the Air Force, 1970; Hislop, 1960). 

In St. Louis, the decision to issue a warning is made at 11 a.m., based on two readings from that morning

and two readings from the previous afternoon. When the average of those readings is above 85EF, a heat

warning is issued accompanied by increased surveillance of emergency rooms to detect increases in heatrelated illnesses or deaths. The next level of warning, a heat alert, requires the opening of cooling

shelters and the notification of the Salvation Army and the American Red Cross. The highest level of

warning, a heat emergency (which can only be activated by the mayor of St. Louis, the St. Louis County

executive, or the governor) is based on information obtained from Operation Weather Survival, the state,

city, and county health departments.

Finding: St. Louis’ Operation Weather Survival, a loose affiliation of agencies involved in

responding to heat emergencies and coordinated by the local chapter of the United Way, developed

an extensive and detailed plan for responding to heat emergencies.

Finding: The St. Louis Heat Response Plan is activated by Heat Warnings jointly issued by the St.

Louis Department of Health and the St. Louis County Health Department, based on readings of a

wet bulb globe thermometer not by Heat Warnings issued by the NWS.
50

NWS Actions

During the July 1995 heat wave, forecasters at the NWS Forecast Office at St. Louis issued high quality

forecasts and statements that informed their community of the dangerous heat wave. Accurate and timely

forecast information was provided as much as 5 days in advance of the excessive heat. Products issued

by NWS forecasters clearly conveyed important and accurate forecast information regarding excessive

temperatures. A Heat Advisory was in effect well prior to and throughout the event. In fact, Heat

Advisories were issued for a consecutive 2-day period. This action, based on sound professional

judgment, conveyed important information on the anticipated duration of this event.

As the event neared, the office issued a variety of frequent, well-written statements that relayed

emergency and safety information to the community. Statements were often targeted to high risk groups. 

NWS forecasters issued a number of extra products that provided climate and other information to the

community. NWS forecasters were also in contact with state, city, and local officials during the event.

Finding: NWS forecasters clearly and accurately communicated the likelihood of unusually high

levels of heat for St. Louis 5 days prior to the event.

Finding: NWS forecasters issued a Heat Advisory for St. Louis for a consecutive 2-day period. 

This action provided community officials with key planning information.

Media Coverage

The St. Louis media recognize the dangers of excessive summer heat and reflect this in their frequent

reporting. The media covered the July 1995 heat wave from both the meteorological and news

perspectives. In fact, the St. Louis media found it difficult to find different story angles as the heat wave

lingered.
51

REFERENCES

Centers for Disease Control and Prevention. "Heat-Related Mortality — Chicago, July 1995." 

Morbidity and Mortality Weekly Report, 1995; 44:577-9.

_________. "Heat-Related Deaths — Philadelphia and United States, 1993-1994." Morbidity

and Mortality Weekly Report, 1994; 43:453-5. 

_________. "Heat-Related Deaths — United States, 1993." Morbidity and Mortality Weekly

Report, 1993; 42:558-560.

Departments of the Army and the Air Force, "Health Problems Related to Extreme

Temperatures," Field Hygiene and Sanitation, 1970; 80-81.

Hislop, Livingstone R., "Technical Notes: The Wet Bulb-Globe Temperature Index." U.S.

Armed Forces Medical Journal, 1960; 11:709-712.

Jones, T.S.; Liang, A.P.; Kilbourne, E.M.; et al. "Morbidity and Mortality Associated with the

July 1980 Heat Wave in St. Louis and Kansas City, Missouri." Journal of the American Medical

Association, 1982; 247:3327-31.

Kalkstein, L.S., "Health and Climate Change: Direct Impacts in Cities." The Lancet, 1993;

342:1397-1399.

_________, "A New Approach to Evaluate the Impact of Climate Upon Human Mortality." 

Environmental Health Perspective; 1991; 96:145-50.

_________, and Davis, R.E., "Weather and Human Mortality: An Evaluation of Demographic

and Inter-regional Responses in the United States." Annals of the Association of American

Geographers, 1989; 79:44-64.

_________, and Smoyer, K.E., "The Impact of Climate Change on Human Health; Some

International Implications." Experientia 49 (1993), Birkhauser Verlag.

_________, and Valimont, K.M., "An Evaluation of Summer Discomfort in the United States

using a Relative Climatological Index." Bulletin of the American Meteorological Society, 1986;

67:842-48.

Kilbourne, E.M., "Heat Waves" in The Public Health Consequences of Disasters (Centers for

Disease Control and Prevention monograph). Atlanta: U.S. Department of Health and Human

Services, Public Health Service, Centers for Disease Control and Prevention, 1989; 51-61.

_________; Choi, K.; Jones, T.S.; Thacker, S.B.; and the Field Investigation Team. "Risk

Factors for Heat Stroke: A Case Control Study." Journal of the American Medical Association,

1982; 247:3332-6.
52

Lee, D.H. "Seventy-five Years of Searching for a Heat Index." Environmental Research, 1980;

22:331-56.

Riebsame, W.E. 1985. "Climate Hazards: Lessons from Recent Events in the United States." 

Disasters; 9:295-300.

_________; Diaz, H.F.; Moses T.; and Price, M. "The Social Burden of Weather and Climate

Hazards." Bulletin of the American Meteorological Society, 1986; 

67:1378-88.
A-1

APPENDIX A

REVIEW CRITERIA FOR NWS PRODUCTS,

SERVICES, AND ACTIONS

In a review of NWS forecast office products and services, both objective and subjective actors

must be considered. Objective actions include compliance with WSOM chapters that serve as

baseline instructions for forecast offices. Subjective factors also play a critical role, especially

during high impact meteorological events. Subjective actions include those actions taken by

forecasters above and beyond what is specified by written guidance.

Objective Review

< General compliance with WSOM Chapter C-44, Non-Precipitation Weather Hazards, and

related guidelines and policies.

< Frequency of statement issuance.

< Accuracy of forecasts.

Subjective Review

A subjective review of forecast office actions is a more complex task. It must consider forecaster

response that at times is based on limited information. It might include the following.

< Appropriateness of actions.

< Recognition of magnitude of event.

< Responsiveness.

< Proper transition from an unusual into a critical weather event.

< Quality of forecasts.

< Quality of statements.

Time Sequence Review

In addition to these objective and subjective factors, this review will be defined further by the

following time sequences.

< Extended Forecast Review: Period of time generally greater than 48 hours prior to the onset

of the excessive heat event.

< Forecast Review: Period of time generally between 36 and 48 hours prior to the onset of the

period of review.

< Short Term Forecast Review: Period of time within the excessive heat event.

< Post-event Review: Period of time after the excessive heat event.