Counties with the coldest winters in Illinois

If you've been jarred by winter weather lately, you're not alone. The winter of 2023-2024 was the warmest recorded in the continental U.S. (records span the past 130 years), with average temperatures 5.4 degrees higher than normal.

At the same time, severe cold snaps are also getting more intense. In January 2025, freezing temperatures stretched down the usually balmy Gulf Coast and brought unprecedented snowfall to Southern states like Louisiana and Florida.

While record-high temperatures and heavy snow might seem contradictory, they're actually symptoms of the same climate phenomenon. In the Arctic, the polar jet stream—which usually creates a boundary between the frigid northern air and the more temperate remainder of the globe—has weakened as a result of greenhouse gas emissions. This has allowed the jet stream to dip further than ever before, leading to cold snaps across the Southern U.S. Those same greenhouse gas emissions are also partly responsible for the warmer winters we've been seeing. So, as counterintuitive as it may seem, warmer winters and extreme cold events go hand-in-hand.

Though typically areas in the Northern U.S. tend to be much colder than their Southern counterparts, even within the same state, temperatures can vary greatly. To determine where temperatures drop the lowest in the winter, Stacker compiled a list of the counties with the coldest winters in Illinois using data from the National Centers for Environmental Information. Data represents the average temperatures from December 2023 to February 2024; the historic average is the average for these months from 1901 to 2000. All temperatures are in Fahrenheit.