Jefferson County Climate
Jefferson County, Missouri
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
55.7°F
Annual Precip
44.1"
Annual Snowfall
9.1"
Extreme Heat Days
38
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
7a
Minimum winter temperature range for plant survival
4,095
Excellent for heat-loving crops
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: Jefferson County
Climate Verdict
Jefferson County has a mild, with an average annual temperature of 55.7°F, moderately wet with 44.1 inches of annual precipitation, occasional hot days — 37.6 per year above 90°F, light snow averaging 9.1 inches per year. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are cold, with January averaging 31.7°F. summers are warm — July averages 77.8°F. The 46°F seasonal variation provides noticeable but manageable change.
Outdoor & Gardening Guidance
The moderate temperatures support hiking, cycling, and camping comfortably in spring, summer, and fall.
Regional Context
Jefferson County closely matches the Missouri statewide average temperature of 54.9°F.
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.
Frequently Asked Questions
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Data sources: NOAA National Centers for Environmental Information (NCEI), U.S. Climate Normals 1991-2020. Forecast and alert data from National Weather Service API. Air quality data from Open-Meteo.
Climate normals are 30-year averages of weather variables. Station data is aggregated to county level. Forecasts and alerts are fetched live and may change frequently. Data is informational only — not a substitute for official National Weather Service forecasts or emergency weather warnings.