One of the most oppressive heat waves since mid July 1995 enveloped Eastern Pennsylvania from July 21st through the 24th. The heat was responsible for twenty-five deaths, twenty-two within Philadelphia and dozens of heat related injuries. Many locations had high temperatures that reached into the 100s. The most oppressive day was July 22nd when the combination of temperature and dew points pushed afternoon heat index values over 105F and neared 120F in Philadelphia.
There were twenty-five heat related deaths in Eastern Pennsylvania, twenty-two in Philadelphia, two in Montgomery County and one in Lehigh County. Most were elderly people with underlying health problems who were found indoors without air-conditioning. There were dozens upon dozens of cases of heat exhaustion and other heat related illnesses. The largest concentration occurred at the Philadelphia Phillies game at Citizen Bank Park on the 22nd.
To combat the heat, many counties, cities and municipalities opened cooling centers. The hours of air-conditioned senior citizen centers were extended. Homeless shelters also extended their hours. County severe weather emergency phone lines were activated. In Philadelphia, the Corporation for Aging had councilors and nurses on the phone through Midnight EDT each day. The city opened sixty cooling centers. Philadelphia schools dismissed early on the 21st and cancelled all classes on the 22nd. People flocked to the malls, movie theaters and pools to keep cool. Construction workers adjusted their work days and started early. Paving work was postponed. Some municipalities enacted burning bans.  Water and electrical service shutoffs were postponed. Home air-conditioning repairs, ice suppliers, automobile air conditioning repairs, chilly treat vendors all saw increases in demand as was an increase in water deliveries.
The heat caused the buckling of U.S, Route 422 near Pottstown in Montgomery County. Utilities urged people to conserve electricity and water while many were setting usage records. Overall there were not many heat related power outages, but a power outage in Chester County forced the evacuation of a drug and rehabilitation center. The PJM Interconnect (manages high voltage transmission systems) which includes Pennsylvania, Delaware, Maryland and New Jersey set an all time record usage of 158,000 megawatts at 5 p.m. EDT on July 21st. Pennsylvania Power and Light set all-time record usage of 7,622 megawatts at 2 p.m. EDT on the 22nd.
The lack of rain along with the heat was stressing both farm crops and livestock.
Highest temperatures (all of which occurred on the 22nd) included 106 degrees in Reading (Berks County), 105 degrees in Pottstown (Montgomery County), 104 degrees at the Lehigh Valley International Airport, 103 degrees at the Philadelphia International Airport and Doylestown (Bucks County), 102 degrees in Quakertown (Bucks County) and 94 degrees in Mount Pocono (Monroe County).  The highest hourly heat index at the Philadelphia International Airport was 119 degrees on the 22nd. No official records on heat index are kept, but it was believed this was the highest hourly heat index in Philadelphia since July 15, 1995.
At the Philadelphia International Airport, the 103 degree high temperature on the 22nd was the hottest day since July 3, 1966 (103 degrees) and the 4th highest maximum temperature on record. The minimum temperature of 83 degrees on the 23rd tied July 24, 2010 with the highest minimum temperature on record.  The monthly average temperature of 82.4 degrees was not only the warmest July on record, but also the warmest month ever. The 21 days in which the maximum temperature reached 90 degrees or high is in a four way tie for the most in any July and any month.
At the Lehigh Valley International Airport, the 104 degree high temperature on the 22nd was the second hottest day on record second only to July 3, 1966 (105 degrees). The minimum temperature of 78 degrees on the 22nd was the second highest minimum temperature on record.  The monthly average temperature of 78.0 degrees tied for the third warmest July on record, but also tied the third warmest month ever.
At the Reading Regional Airport, the monthly average temperature of 80.4 degrees was the second warmest July and month on record to 1955 (81.5 degrees).  The 20 days in which the maximum temperature reached 90 degrees or high tied with 1955 and 1999 as the most for any July or any month.  At the Pocono Municipal Airport in Mount Pocono, the monthly average temperature of 71.9 degrees was the second warmest July and month on record only surpassed by 1949 (72.5 degrees).
This heat wave helped make July 2011 the sixth hottest July on record for the state of Pennsylvania with a statewide average temperature of 74.4 degrees.
A weak cold front ended the heat wave on the 25th.

Excessive Heat in CARBON, PENNSYLVANIA
From 21-JUL-11 09:00:00 to 22-JUL-11 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in MONROE, PENNSYLVANIA
From 21-JUL-11 09:00:00 to 22-JUL-11 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in BERKS, PENNSYLVANIA
From 21-JUL-11 09:00:00 to 24-JUL-11 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in NORTHAMPTON, PENNSYLVANIA
From 21-JUL-11 09:00:00 to 24-JUL-11 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in LEHIGH, PENNSYLVANIA
From 21-JUL-11 09:00:00 to 24-JUL-11 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in CHESTER, PENNSYLVANIA
From 21-JUL-11 09:00:00 to 24-JUL-11 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in BUCKS, PENNSYLVANIA
From 21-JUL-11 09:00:00 to 24-JUL-11 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in DELAWARE, PENNSYLVANIA
From 21-JUL-11 09:00:00 to 24-JUL-11 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in PHILADELPHIA, PENNSYLVANIA
From 21-JUL-11 09:00:00 to 24-JUL-11 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in MONTGOMERY, PENNSYLVANIA
From 21-JUL-11 09:00:00 to 24-JUL-11 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS