Great Lakes Region

La Niña Impacts| November 2017 

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

Great Lakes

November 2017

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 plunges 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 closely along the Pacific Northwest, 

bringing increased chances for moisture. Finally, odds increase 

slightly for wetter-than-normal conditions in the Ohio River valley.

The result for the Great Lakes is that odds shift toward chances 

to be cooler than normal, especially in the western Great Lakes 

area. The southern Great Lakes, near the Ohio River valley, also 

may see a slight shift toward wetter-than-normal conditions. 

Finally, there is evidence that weak La Niñas favor more ice cover 

especially when coupled with other large-scale climate influences 

that are only predictable on much shorter time scales.

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 

strengthened enough to reach a weak La Niña phase as 

predicted when the sea surface temperature anomalies 

surpassed −0.5°C on the Oceanic Niño Index (ONI). The La Niña 

conditions are predicted to continue at least through winter. 

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 toward neutral (green bars) in late spring through the 

summer months. El Niño (red bars) chances increase through 

the summer as well but remain relatively small. This is a typical 

evolution of the ENSO pattern. For more information please 

visit:

http://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/

Precipitation and Temperature

The Great Lakes straddles the boundary of temperature conditions, with 

slightly increased chances for colder temperatures in the far western portion 

of the basin, equal chances for above-, below-, or neutral temperatures across 

the central lakes, and an increased chance of warmer temperatures near the 

eastern lakes. Note that these chances are quite small because of uncertainty in 

the strength and position of the La Niña as well as other potential influences.

For precipitation, the outlook indicates greater chances for wetter-than-normal 

conditions over the Great Lakes and surrounding areas.

The temperature and precipitation outlooks are consistent with a more active 

storm track across the region this winter, leading to more cold outbreaks and 

precipitation chances. The outlook is complicated by the likely weakness of 

the La Niña, as well as the potential for other climate effects to play a larger 

role from time to time. The La Niña impacts will likely reach their climax during 

winter and then slowly ebb as spring approaches. Please visit the Climate 

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

Temperature

Valid for Dec 2017–Feb 2018. A: Above normal; B: Below normal;

EC: Equal chances for above-, below-, or near-normal

Precipitation
Contact: Doug Kluck (doug.kluck@noaa.gov) Great Lakes Region

La Niña Impacts | November 2017

Climate Impacts

La Niña has worldwide impacts on the 

agricultural sector. For the Great Lakes, most 

of the impacts are felt in winter. Winters 

associated with La Niña tend to be cold with 

above-average precipitation and could negatively impact winter wheat and fruit orchards. 

However, because La Niña winters typically 

result in increased snowpack in the Great 

Lakes, this could insulate these crops to the 

cold air outbreaks and harsh wind. Harsher 

winter temperatures could be negative for 

livestock producers due to increased operating 

costs and potential stress on animals. La Niña 

could affect commodity prices due to negative 

impacts internationally.

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 

home heating costs, costs associated with 

snow removal, and difficulties in overland 

transportation. Sectors that depend on winter 

weather conditions will likely see a benefit 

from increased snowfall. These include winter 

recreation, snow removal businesses, towing 

companies, and road salt sales. In addition, 

more ice on the Great Lakes could mean 

the potential exists for a delayed navigation 

season for shipping in the spring.

The images above show the differences from the mean in the last weak La Niña event from the winter 

of 2000–2001 (December–February). 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 

this winter. As mentioned previously, short-term climatic influences that are not predictable beyond 

a week or two can play havoc with the seasonal 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:

The potential for increased snowpack 

accumulation leads to a better chance for 

more runoff into the lakes during the spring, 

when runoff is typically a major contributor to 

a seasonal rise in water levels. With potentially 

more ice on the lakes later in the winter due to 

cooler-than-normal conditions, less evaporation 

may occur when compared to a winter when 

the lakes are mostly ice free. Increased runoff 

and decreased evaporation could act to take 

less water away from the system than normal. 

These combined factors could lead to higher 

lake levels into next season. Finally, with 

the increase in chances for above-normal 

precipitation the likelihood of greater snow 

accumulations are greater as well.

Comparisons and Limitations

National Oceanic and Atmospheric Administration

www.noaa.gov 

National Centers for Environmental Information

www.ncei.noaa.gov

Great Lakes Environmental Research Laboratory

www.glerl.noaa.gov

Climate Prediction Center

www.cpc.noaa.gov 

Office for Coastal Management

http://coast.noaa.gov/ 

NOAA Great Lakes Sea Grant Network

www.seagrant.noaa.gov 

Great Lakes Integrated Sciences & Assessments

www.glisa.umich.edu 

U.S. Army Corps of Engineers, Detroit District

www.lre.usace.army.mil 

American Association of State Climatologists

www.stateclimate.org 

National Integrated Drought Information System

www.drought.gov

Midwestern Regional Climate Center

http://mrcc.illinois.edu 

USDA Midwest Climate Hub 

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

Accumulated Precipitation (%) Departure from Mean Temperature (° F)

Departure from mean tempearture (left) and percent of mean percipitation (right) during the La Niña 

winter of 2000-2001. Maps courtesy of the Midwestern Regional Climate Center

Image courtesy of: Mark Longstroth, Michigan State Extension Image courtesy of: Illinois-Indiana Sea Grant Image courtesy of: Illinois-Indiana Sea Grant

Great Lakes Partners

No Two La Niñas Are the Same 

La Niña impacts can be limited by many factors, including:

• It may not fully develop and thus not influence the weather as much.

• It may be weak, with little or no discernible influence on weather patterns.

• It may be overcome by other weather and climate events which dampen the 

impacts.

• One or two extreme events can cause the average precipitation or 

temperature for the winter to appear differently than the rest of the season.

La Niña can affect some temperature and precipitation signals in the 

region, but 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 flooding events in the spring.

Agriculture Economic Water Levels and Lake Ice