Massac County Climate
Massac County, Illinois
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
57.3°F
Annual Precip
50.2"
Annual Snowfall
3.1"
Extreme Heat Days
42
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
7a
Minimum winter temperature range for plant survival
4,362
Excellent for heat-loving crops
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: Massac County
Climate Verdict
Massac County has a mild, with an average annual temperature of 57.3°F, moderately wet with 50.2 inches of annual precipitation, occasional hot days — 41.5 per year above 90°F, light snow averaging 3.1 inches per year. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are cold, with January averaging 34.1°F. summers are warm — July averages 78.4°F. The 44°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
Massac County is 4.5°F warmer than the Illinois statewide average of 52.8°F, it is also noticeably wetter, receiving 8.5 inches more precipitation than the state average.
Climate Profile
About Massac County Weather
A Warm Southern Illinois Climate Profile
Massac County is significantly warmer than the national median with an annual average of 57.3°F. It experiences a humid subtropical influence that is rare for the rest of the state.
One of Illinois' Warmest and Wettest
Massac's 57.3°F average far exceeds the state average of 52.8°F, placing it among the warmest Illinois counties. It also receives 50.2 inches of rain, well above the state's 41.7-inch norm.
Vastly Different Weather Than Northern Peers
Compared to northern counties like McHenry, Massac sees almost no snow, averaging just 3.1 inches annually. It also endures 42 days of extreme heat, the highest in this regional set.
Mild Winters and Intense Summer Heat
The county sees a sweltering 42 days above 90°F, with July averages reaching 78.4°F. Winters are much milder than the rest of Illinois, staying well above freezing with a 36.6°F average.
Prioritize Cooling and Storm Preparedness
High-capacity air conditioning is vital to handle the six weeks of extreme heat days. Because the county receives over 50 inches of rain, ensure your property has excellent drainage and gutter systems.
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.