Jefferson County Climate
Jefferson County, Missouri
Avg Annual Temp
55.7°F
Annual Precip
44.1"
Annual Snowfall
9.2"
Extreme Heat Days
37.6
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Seasonal Overview
National Comparison
Climate Profile
About Jefferson County Weather
Moderate Temperatures in Jefferson County
Jefferson County maintains a 55.7°F annual average temperature, placing it slightly above the national median. It enjoys a temperate climate with a generous 44.1 inches of annual precipitation.
Warmer Than the Missouri Average
At 55.7°F, Jefferson County is nearly a degree warmer than the Missouri state average of 54.9°F. Its precipitation levels are essentially on par with the state average of 43.8 inches.
A Warm Corridor South of St. Louis
Jefferson County is warmer than Jackson County by 1.5 degrees on average. It experiences 38 days of extreme heat, which is higher than the 33 days recorded in the Kansas City area.
Consistent Rainfall and Humid Summers
The county averages 38 days above 90°F, with July temperatures averaging a warm 77.8°F. Winter brings a modest 9.1 inches of snow and an average temperature of 34.4°F.
Plan for Humidity and Summer Spikes
Residents should prepare for humid summers by ensuring dehumidifiers and AC units are in top shape. The 9.1 inches of annual snow is light, but the 44.1 inches of rain suggests keeping rain gear handy year-round.
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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.