Climate change in McHenry County, Illinois
Since 1979, McHenry County, Illinois has warmed 2.4°F, with 3 more days above 90°F, about the same number of nights above 70°F and 5% more precipitation a year. Its climate in 1996–2025 is most like Porter County, IN's was in 1951–1980.
- Average temperature: +2.4°F
- Summer highs (Jun–Aug): +1.5°F
- Winter lows (Dec–Feb): +3.9°F
- Precipitation: +5%
- Wettest day of the year: +15%
- Longest dry spell: −3 days
- Days above 90°F: +3 days
- Nights above 70°F: +0 days
- Freezing nights: −8 days
- Frost-free season: +7 days
- Muggy days: +0 days
- Summer heat index (Jun–Aug): +1.9°F
- Extreme fire-weather days: +17 days
- Snowfall: +24%
- Snowy days (1 inch or more): +3 days
Changes follow the trend line through every year from 1979 to 2025. Data: NOAA nClimGrid-Daily; humidity from gridMET, adjusted to airport observations.