Marion County Climate
Marion County, Illinois
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
54.8°F
Annual Precip
44.9"
Annual Snowfall
10.9"
Extreme Heat Days
32
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
6b
Minimum winter temperature range for plant survival
3,966
Supports most vegetables & fruits
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: Marion County
Climate Verdict
Marion County has a mild, with an average annual temperature of 54.8°F, moderately wet with 44.9 inches of annual precipitation, occasional hot days — 32.45 per year above 90°F, light snow averaging 10.9 inches per year. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are cold, with January averaging 29.7°F. summers are warm — July averages 77.2°F. The 47°F seasonal variation provides noticeable but manageable change.
Outdoor & Gardening Guidance
Growing season and gardening data is currently limited for Marion County. Check the USDA Plant Hardiness Zone Map and local extension office for specific guidance.
Regional Context
Marion County closely matches the Illinois statewide average temperature of 52.8°F, it is somewhat wetter than average for Illinois.
Climate Profile
About Marion County Weather
Warm and Exceptionally Wet
Marion County's 54.8°F annual average temperature is notably higher than the national median. It stands out for its 44.9 inches of annual precipitation, making it one of the wetter regions in the state.
A Leader in Statewide Rainfall
Marion County's 44.9 inches of rain significantly exceeds the Illinois state average of 41.7 inches. Its 54.8°F annual average also places it well above the state mean of 52.8°F.
Sizzling Summer Heat Days
Marion faces 32 days of extreme heat over 90°F, more than Madison or Macoupin. It also has one of the lowest snowfall totals in the region at just 10.9 inches.
Long Summers and Brief Snow
The July average is a sultry 77.2°F, fueling over a month of extreme heat days. Winters remain relatively warm, with the December-February average staying above freezing at 32.7°F.
Water Management and Heat Relief
Homeowners must plan for high moisture levels and potential localized flooding due to the 44.9-inch rain total. Cooling systems will be heavily utilized during the 32 days of extreme annual heat.
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.