Climate change in Jefferson County, Iowa
Since 1979, Jefferson County, Iowa has warmed 0.9°F, with 9 fewer days above 90°F, about the same number of nights above 70°F and 1% less precipitation a year. Its climate in 1996–2025 is most like McDonough County, IL's was in 1951–1980.
- Average temperature: +0.9°F
- Summer highs (Jun–Aug): −1.2°F
- Winter lows (Dec–Feb): +2.5°F
- Precipitation: −1%
- Wettest day of the year: +33%
- Longest dry spell: −4 days
- Days above 90°F: −9 days
- Nights above 70°F: −0 days
- Freezing nights: +1 days
- Frost-free season: −7 days
- Muggy days: +5 days
- Summer heat index (Jun–Aug): −0.6°F
- Extreme fire-weather days: +6 days
- Snowfall: −13%
- Snowy days (1 inch or more): +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.