Climate change in Union County, Illinois
Since 1979, Union County, Illinois has warmed 2.5°F, with 3 fewer days above 90°F, 17 more nights above 70°F and 3% more precipitation a year. Its climate in 1996–2025 is most like Carlisle County, KY's was in 1951–1980.
- Average temperature: +2.5°F
- Summer highs (Jun–Aug): −0.7°F
- Winter lows (Dec–Feb): +5.0°F
- Precipitation: +3%
- Wettest day of the year: −1%
- Longest dry spell: +2 days
- Days above 90°F: −3 days
- Nights above 70°F: +17 days
- Freezing nights: −23 days
- Frost-free season: +24 days
- Muggy days: +11 days
- Summer heat index (Jun–Aug): −0.1°F
- Extreme fire-weather days: +1 days
Changes follow the trend line through every year from 1979 to 2025. Data: NOAA nClimGrid-Daily; humidity from gridMET, adjusted to airport observations.