Winters in Illinois are changing. Every ten years, the USDA releases a new Plant Hardiness Zones map which shows the average annual extreme winter temperatures throughout the United States and Puerto Rico. The most recent map, released at the end of 2023, showed that winter in Illinois is getting warmer. Illinois State Climatologist shares winters are warming at a faster rate than the other seasons.
“One of the impacts of this is a reduction in the frequency and the intensity of extreme cold in the wintertime. All across the state, we still get very cold temperatures. We set the statewide all-time low temperature record in 2019 up in Mount Carroll, but the frequency and the length, the duration the intensity of that cold is decreasing.”
The Plant Hardiness Zones map breaks the United States into 13 temperature zones. Each zone is broken into half zones to help identify shifts in temperature data. In the 2023 map, USDA reports that half of the United States saw a northern shift of a half zone, meaning warmer temperatures moved further north.
These maps are one of the tools USDA offers to help growers determine what plants can thrive in different areas of the country. Ford adds animals and plants that might not do well in extreme cold temperatures, have better chances of survival.
“On the flip side, problems that come from a decrease in that extreme cold are many. We talked about how there are certain plants and animals that can thrive in a little bit of a warmer Illinois winter., well some of those plants and animals are non-native and invasive or problematic. And we’re seeing that these non-native invasive species of plants and animals are migrating further to the north and bringing with them either competition for our culturally or economically important species of plants and animals.”
Ford adds that the 2023 map showed some historically southern weather zones in southern Illinois.