Marion County Climate
Marion County, Illinois
Avg Annual Temp
54.8°F
Annual Precip
44.9"
Annual Snowfall
10.8"
Extreme Heat Days
32.45
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Seasonal Overview
National Comparison
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 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.