Climate change in Marion County, Illinois
Since 1979, Marion County, Illinois has warmed 2.5°F, with 2 fewer days above 90°F, 4 more nights above 70°F and 16% more precipitation a year. Its climate in 1996–2025 is most like Posey County, IN's was in 1951–1980.
- Average temperature: +2.5°F
- Summer highs (Jun–Aug): −0.4°F
- Winter lows (Dec–Feb): +4.4°F
- Precipitation: +16%
- Wettest day of the year: +22%
- Longest dry spell: −3 days
- Days above 90°F: −2 days
- Nights above 70°F: +4 days
- Freezing nights: −18 days
- Frost-free season: +11 days
- Muggy days: +7 days
- Summer heat index (Jun–Aug): +0.4°F
- Extreme fire-weather days: +4 days
Changes follow the trend line through every year from 1979 to 2025. Data: NOAA nClimGrid-Daily; humidity from gridMET, adjusted to airport observations.