Fall temperatures have finally arrived in Chicago after weeks of sweltering heat and humidity. The sharp drop-off in temps comes with the return of a familiar weather phenomenon—the La Niña effect.
The weather pattern means colder air in the Northern Hemisphere and the potential for more snow in Chicago this winter. In fact, the La Niña effect has coincided with some of the Windy City’s biggest historical snowstorms.
So just how strong will the effect be this season? Could winter 2025-26 mean Chicago is in for Snowmaggedon: The Sequel? Here’s everything to know!
Understanding La Niña
La Niña conditions surfaced in late September according to the National Weather Service’s (NWS) Climate Prediction Center. The phenomenon is marked by below-average sea temperatures near the Pacific equatorial region.
While the cooler ocean temperatures occur thousands of miles away, they majorly influence weather outcomes in Chicago. La Niña typically brings wetter and snowier winter conditions to the upper Midwest.
The intensity of La Niña can vary—the stronger the effect, the greater the chance for heavy snowfall.
The 2025-26 winter outlook
The NWS anticipates the current La Niña pattern to remain in the weaker range, but this could change over the course of the fall through winter season. The phenomenon will stick around through February 2026 according to predictions.
Additionally, a marine heatwave or “warm blob” is predicted to form this winter which could increase the chances for heavy snowfall in Chicago even further!
If the predictions are any indication, the coming winter could be a doozy. So break out your winter coats and keep a snow shovel handy Chicago—we’ve got a long couple of months ahead!