La Niña Winter Likely: Here's What It Means For Illinois

ILLINOIS — With cooler temperatures to start for September, many Chicagoans may be wondering about even colder temperatures ahead. What does the winter look like for the Chicago area? Are we in for milder temperatures, or will we see snowy days?

The answer may lie with La Niña, the National Oceanic and Atmospheric Administration announced this month. The National Oceanic and Atmospheric Administration has issued a La Niña Watch for the fall and early winter of 2025-26, meaning there is at least a 50 percent chance of a weak La Niña developing later this year.

La Niña is a climate phenomenon that occurs when the central and eastern Pacific Ocean cools down more than usual. It typically causes the northern United States to be cold and wetter than usual, and the southern states to be warmer and drier than usual. That pattern generally extends to Illinois as well. In La Niña conditions, Illinois is usually colder and wetter than normal.

El Niño, on the other hand, usually means the reverse. The central and eastern Pacific warms up more than usual, resulting in warmer weather in the north, wetter weather in the south, and often large, unpredictable storms.

Currently, the Pacific remains in ENSO-neutral conditions, meaning neither La Niña nor El Niño are active, but NOAA’s latest predictions expect that to shift around October.

"ENSO-neutral is most likely through the late Northern Hemisphere summer 2025 (56 percent chance in August-October)," the National Oceanic and Atmospheric Administration announced. "Thereafter, a brief period of La Niña conditions is favored in the fall and early winter 2025-26 before reverting to ENSO-neutral."

According to their August 14 predictions, experts say that there is around a 55 percent chance La Niña will develop any time from September to November.

La Niña often means a wetter winter in Illinois, and the seasonable precipitation outlook for November-January supports this. The National Oceanic and Atmospheric Administration maps show a "leaning above chance" that much of Illinois will see seasonal precipitation 33 to 40 percent above normal. Experts are also saying that there is a "leaning above" chance that temperatures will be leaning above normal.

Nationwide

Much of the southern U.S., stretching from California’s Central Coast to Florida and up the entire East Coast, is moderately likely to see above-average temperatures this winter.

Much of the southern U.S., stretching from the Bay Area in a U-shape to the Washington D.C. area, is moderately likely to see below-average precipitation. Pockets of the Midwest, including Indiana, Ohio, and Kentucky, and much of Montana, Wyoming, and Alaska, are 33-40% likely to see above-average participation. The rest of the country remains uncertain.

On that note, much of this forecast remains relatively uncertain. “Nothing is guaranteed in this business,” said Michelle L’Heureux, scientist at the National Weather Service’s Climate Prediction Center.

NOAA updates its long-range outlooks monthly, and the next forecast is scheduled for Sept. 19. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center website. See here for predictions through November 2026.