Jefferson County Climate
Jefferson County, Iowa
Avg Annual Temp
49.7°F
Annual Precip
38.4"
Annual Snowfall
21.7"
Extreme Heat Days
23.8
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Seasonal Overview
National Comparison
Climate Profile
About Jefferson County Weather
Jefferson's Warm Humid Continental Climate
Jefferson County averages 49.7°F annually, sitting below the national median but among the warmer spots in Iowa. It features a lush environment supported by 38.4 inches of rain.
Warmer and Wetter than Average
The county stays nearly two degrees warmer than the Iowa state average of 48.0°F. It also receives about two extra inches of precipitation compared to the 36.1-inch state norm.
High Heat Relative to Neighbors
Jefferson sees 24 extreme heat days per year, significantly more than the 16 days recorded in nearby Keokuk County. It remains warmer and wetter than central Iowa counties like Jasper.
Milder Winters and Toasty Summers
Winters are relatively mild for the region, averaging 25.4°F with 21.7 inches of snow. However, summers are intense, featuring 24 days where the mercury hits 90°F or higher.
Focus on Cooling and Drainage
The high number of extreme heat days makes efficient air conditioning a top priority. Homeowners should also maintain clear gutters to handle the heavy 38.4 inches of annual rainfall.
Frequently Asked Questions
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Data source: NOAA National Centers for Environmental Information (NCEI), U.S. Climate Normals 1991-2020.
Climate normals are 30-year averages of weather variables computed from 1991 to 2020. Station data is aggregated to county level using spatial averaging. Data is informational only — not a substitute for official National Weather Service forecasts or emergency weather warnings.