Clay County Climate
Clay County, Illinois
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
55.5°F
Annual Precip
47.0"
Annual Snowfall
10.2"
Extreme Heat Days
40
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
6b
Minimum winter temperature range for plant survival
4,089
Excellent for heat-loving crops
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: Clay County
Climate Verdict
Clay County has a mild, with an average annual temperature of 55.5°F, moderately wet with 47.0 inches of annual precipitation, occasional hot days — 39.8 per year above 90°F, light snow averaging 10.2 inches per year. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are cold, with January averaging 30.9°F. summers are warm — July averages 77.3°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
Clay County closely matches the Illinois statewide average temperature of 52.8°F, it is also noticeably wetter, receiving 5.2 inches more precipitation than the state average.
Climate Profile
About Clay County Weather
Warmer and wetter than the national median
Clay County is warmer than the national median, boasting an annual average temperature of 55.5°F. Its 47.0 inches of annual precipitation makes it one of the wetter regions in the American Midwest.
Among the warmest spots in Illinois
Ranking well above the state average of 52.8°F, Clay is among the warmest counties in southern Illinois. It also exceeds the state’s average rainfall by over five inches per year.
Outpacing Clinton County in extreme heat
Clay’s 40 extreme heat days per year outpace the 32 days seen in neighboring Clinton County. However, both counties share similar winter profiles with approximately 10 inches of annual snowfall.
Intense summer heat with mild winters
Summer is intense here, with 40 days hitting 90°F or higher and a July average of 77.3°F. Winters are the mildest in this group, with a January average of 30.9°F and just 10.2 inches of snow.
Maximize HVAC efficiency for high heat
Residents should invest in high-efficiency HVAC systems to manage the 40 days of extreme summer heat. Outdoor gear should focus on rain protection given the heavy 47-inch annual precipitation total.
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.