Mason County Climate
Mason County, Illinois
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
52.1°F
Annual Precip
40.1"
Annual Snowfall
20.4"
Extreme Heat Days
31
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
6a
Minimum winter temperature range for plant survival
3,574
Supports most vegetables & fruits
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: Mason County
Climate Verdict
Mason County has a mild, with an average annual temperature of 52.1°F, moderately wet with 40.1 inches of annual precipitation, occasional hot days — 31.099999999999998 per year above 90°F, moderate snowfall of 20.4 inches annually. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are very cold — January averages 24.8°F. summers are warm — July averages 75.8°F. Residents experience a substantial 51°F difference between winter and summer.
Outdoor & Gardening Guidance
Growing season and gardening data is currently limited for Mason County. Check the USDA Plant Hardiness Zone Map and local extension office for specific guidance.
Regional Context
Mason County closely matches the Illinois statewide average temperature of 52.8°F.
Climate Profile
About Mason County Weather
Moderate Temperatures in the Heart of Illinois
Mason County averages 52.1°F annually, aligning closely with the national median for the interior United States. This climate produces standard seasonal transitions and a balanced weather profile.
Slightly Cooler Than the State Average
At 52.1°F, Mason County is just a fraction cooler than the 52.8°F Illinois average. Its 40.1 inches of annual rainfall also trails the state benchmark of 41.7 inches slightly.
Higher Heat Frequency Than Nearby Counties
Mason experiences 31 extreme heat days annually, more than neighbors like Marshall or Menard. However, its 20.4 inches of snow is fairly consistent with other central Illinois regions.
A Cycle of Heat and Frost
July brings a warm average of 75.8°F, while January dips to a chilly 24.8°F. The county sees a full month of days exceeding 90°F, making for a long summer season.
Manage High Heat and Winter Chill
Plan for 31 days of temperatures over 90°F by optimizing your home's cooling efficiency. Salt and winter tires are essential for navigating the 20.4 inches of average annual snowfall.
Frequently Asked Questions
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Track your own weather in Mason County
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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.