Hamilton County Climate
Hamilton County, Illinois
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
55.4°F
Annual Precip
47.1"
Annual Snowfall
13.3"
Extreme Heat Days
43
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
6b
Minimum winter temperature range for plant survival
4,039
Excellent for heat-loving crops
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: Hamilton County
Climate Verdict
Hamilton County has a mild, with an average annual temperature of 55.4°F, moderately wet with 47.1 inches of annual precipitation, occasional hot days — 42.6 per year above 90°F, light snow averaging 13.3 inches per year. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are cold, with January averaging 31.6°F. summers are warm — July averages 77.5°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
Hamilton County closely matches the Illinois statewide average temperature of 52.8°F, it is also noticeably wetter, receiving 5.3 inches more precipitation than the state average, the county experiences 15.338967803030304 more extreme heat days than the state average.
Climate Profile
About Hamilton County Weather
Warm and Wet Southern Climate
Hamilton County's 55.4°F annual average temperature is warmer than the national median. Its climate is characterized by significant rainfall and prolonged summer heat.
One of Illinois' Warmest Counties
Averaging 55.4°F, Hamilton is nearly three degrees warmer than the Illinois state average of 52.8°F. It is consistently among the top tier for heat in the state.
Maximum Precipitation in the Region
With 47.1 inches of annual precipitation, Hamilton is much wetter than the state average of 41.7 inches. It shares this humid, high-rainfall profile with neighbor Gallatin County.
Intense Heat and Minimal Snow
The county endures 43 extreme heat days per year where temperatures exceed 90°F. In contrast, it receives only 13.3 inches of snow, making for relatively easy winters.
Beat the Southern Illinois Heat
With over 40 days of extreme heat, robust air conditioning is a non-negotiable for safety and comfort. Homeowners should also ensure property drainage can handle the heavy 47.1-inch rainfall.
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.