Midwest Region

La Niña Impacts| November 2017 

Contact: Doug Kluck (doug.kluck@noaa.gov) 

La Niña Impacts 

and Outlook

A La Niña develops when sea surface temperatures in the 

equatorial Pacific Ocean are cooler than average for an 

extended period of time. This affects the location of jet 

streams, causing impacts in North America. The most notable 

impacts occur in the winter, when the wind patterns in the 

atmosphere are strongest. 

While no two La Niña events are alike, the typical winter 

weather pattern (image) brings the polar jet stream into Alaska, 

then plunging into the central and eastern United States. This 

path can bring colder-than-normal temperatures into the 

northern United States, especially the northern Rockies across 

the northern plains and into the Great Lakes. Meanwhile, 

the southern Great Plains often are left warm and dry. The 

Pacific jet stream tends to track close to the Pacific Northwest, 

bringing increased chances for moisture there. Finally, odds 

increase slightly for wetter-than-normal conditions in the Ohio 

River valley.

The result for the Midwest is that odds shift toward chances to 

be cooler than normal, especially in upper Midwest and Great 

Lakes area. The Ohio River valley, also may see a slight shift 

toward wetter-than-normal conditions.

Typical La Niña Winter Pattern

Winter Outlook

Typical impacts of La Niña on U.S. winter temperature and precipitation. Such impacts have 

been associated with past episodes, but all impacts aren't seen with every episode. NOAA 

Climate.gov drawing by Fiona Martin. (Image Source: NOAA Climate.gov) For more information 

please visit: https://www.climate.gov/news-features/department/enso-blog

La Niña Evolution

La Niña conditions emerged in the fall of 2017. 

Conditions reached a weak La Niña phase when the 

sea surface temperature anomalies surpassed −0.5°C 

on the Oceanic Niño Index (ONI). The current La Niña 

episode is predicted to last through the winter with 

neutral conditions likely to return in the spring. The 

bar chart shows the likelihood of La Niña, El Niño, 

and neutral conditions over the upcoming seasons. 

The odds are highest for La Niña (blue bars) through 

winter. The highest odds shift to neutral (green bars) 

in spring and continue through the summer season. El 

Niño (red bars) chances increase through the summer 

as well, but remain less likely than neutral conditions. 

Over the time period shown, the forecast approaches 

the climatological probabilities for all three categories. 

For more information please visit:

http://iri.columbia.edu/our-expertise/climate

/forecasts/enso/current/

 Midwest

November 2017

Precipitation and Temperature Outlook

Despite the relative weakness of the forecasted La Niña, the 

winter outlook for the Midwest largely follows typical La Niña 

patterns noted in the section above. 

The Midwest straddles the boundary of temperature 

conditions in the outlook, with slightly increased chances for 

colder temperatures to the northwest and slightly increased 

chances of warmer temperatures across the southern edge of 

the region. This outlook is very similar to the typical La Niña 

temperature pattern.

For precipitation, the outlook indicates wetter than normal 

conditions possible for much of the Midwest including the 

Ohio River Basin and over the Great Lakes. Equal chances 

for below-, near-, or above-normal precipitation are likely in 

the southwestern parts of the Midwest region. This outlook 

is largely consistent with the typical La Niña precipitation 

pattern. 

The temperature and precipitation outlooks are consistent 

with a more active storm track across the northern portions 

of the region this winter, leading to more cold outbreaks 

and precipitation chances. Complicating the outlook are the 

likely weakness of the La Niña, as well as the potential for 

other climate effects (such as the North Atlantic Oscillation) 

to play a larger role from time to time. This and other 

influences can overwhelm the La Niña pattern and are much 

more difficult to forecast. The La Niña impacts will likely be 

strongest during the winter and then slowly ebb in spring. 

For more information on the outlooks please visit the Climate 

Prediction Center at: http://www.cpc.ncep.noaa.gov

Outlook for Dec 2017–Feb 2018

A: Above normal

B: Below normal 

EC: Equal chances for above-, 

below-, or near-normal

Temperature

Precipitation
National Oceanic and Atmospheric Administration

www.noaa.gov

National Weather Service - Central Region

www.crh.noaa.gov/crh

National Centers for Environmental Information

www.ncei.noaa.gov

Climate Prediction Center

www.cpc.ncep.noaa.gov

Midwestern Regional Climate Center

mrcc.illinois.edu

National Drought Mitigation Center

www.drought.unl.edu

National Integrated Drought Information System

www.drought.gov

American Association of State Climatologists

www.stateclimate.org

U.S. Department of Agriculture Regional Climate Hubs

www.climatehubs.oce.usda.gov/hubs/midwest

International Research Institute for Climate and Society

http://iri.columbia.edu

Contact: Doug Kluck (doug.kluck@noaa.gov) Midwest Region

La Niña Impacts | November 2017

Climate Outlooks from NOAA's Climate Prediction Center

Agriculture

La Niña has worldwide impacts to the agricultural sector, 

which can influence markets. Locally, agricultural issues 

are less direct because the major La Niña impact occurs 

in winter, outside the main growing season. Winters 

associated with La Niña are often colder than normal with 

above average precipitation, which can negatively impact 

fall seeded crops that must overwinter and perennials 

such (e.g. alfalfa, fruit orchards). The overall impact is 

complicated by snow cover. Snow cover can protect the 

crop while open conditions with severe cold are more 

problematic. Harsh winter temperatures can be adverse 

to livestock producers through increased operating costs, 

potential stress to animals and snow removal issues. The 

cold would be beneficial to the large amount of corn 

being stored on the ground. Another benefit of colder 

than normal temperatures would be to limit certain pests 

(insects and plants) and diseases.

Economic

Cold and wet winters with above-average 

snowfall can have sector-specific impacts 

on the economy. The largest negative 

impacts associated with La Niña are 

increases in heating costs, costs associated 

with snow removal, and difficulties in 

transportation. Sectors that depend on 

having winter weather will likely see a 

benefit from increased snowfall. These 

include winter recreation, snow removal 

businesses, towing companies, and road 

salt sales. Colder and snowier conditions 

could also hamper winter construction in 

the region.

No Two La Niñas Are the Same

The images on the left show the differences 

from mean conditions (December 2000–

February 2001) during the last weak La Niña 

event that lasted through the winter season. 

In many ways, the cooler-than-normal 

temperatures and mainly wetter conditions 

across much of the Midwest and Great Lakes is 

typical. There is no guarantee this or anything 

close to it will be the pattern this year. There 

are limits to our predictability of La Niña 

impacts. As mentioned previously short-term 

climatic influences, that are not predictable 

beyond a week or two, can play havoc with the 

three-month forecasts and can overshadow the 

“typical” La Niña pattern. Even the strength 

of the La Niña (weak versus strong) has an 

influence on whether temperatures will be cold 

or warm in some cases. 

Below are some additional common limiting 

factors of La Niña:

• It may not fully develop.

• It may be weak, with little or no discernible 

influence on weather patterns.

• It may be masked by other weather and 

climate signals.

• Single extreme events can “buck the trend” 

of the averages for the rest of the season, with 

one or two high-impact events overshadowing 

the average conditions. 

Ecosystems and Rivers

Similar to the potential issues with livestock, 

more severe winter conditions could be 

detrimental to wildlife but beneficial to others 

that depend on very cold temperatures. 

The overall availability to water is complex 

with widely varying soil conditions around 

the Midwest. Early winter precipitation on 

unfrozen soils would be beneficial, while snow 

on the wet soils could add to the potential 

flooding in the spring. With a slight abovenormal in chance for precipitation this winter 

across the upper Midwest, the situation will 

have to be monitored closely for greater 

chances for flooding this spring. 

Comparisons and Limitations

Departure from mean temperature (top) and 

percent of mean precipitation (bottom) for the 

winter, Dec 2000-Feb 2001. Maps courtesy of 

the Midwestern Regional Climate Center.

Midwest Partners 

While La Niña can affect some temperature and 

precipitation signals in the region, it is not known to 

affect:

• First freeze date in the fall (either early or late).

• Last freeze date in the spring (either early or late).

• Potential for ice storms or blizzards.

• Track or intensity of any single weather system.

• Potential for drought or flood events in the spring.

Image courtesy of: Jeff Vanuga, NRCS/USDA

Feeding cattle in winter.

Image courtesy of: Roger Hill, NRCS/USDA

Frost and ice form a conservation barrier.

Image credit: ©iStockPhoto.com/FLDphotos

Traffic jam due to snow.

©iStockPhoto.com/FLDphotos

Departure from Mean

Temperature (° F)

Accumulated

Precipitation (%)