Mason County Climate
Mason County, Illinois
Avg Annual Temp
52.1°F
Annual Precip
40.1"
Annual Snowfall
20.4"
Extreme Heat Days
31.1
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Seasonal Overview
National Comparison
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
What is the average temperature in Mason County?
How much rain does Mason County get?
Does it snow in Mason County?
How hot does Mason County get in summer?
How cold are winters in Mason County?
Track your own weather in Mason County
Ambient Weather personal weather stations give you hyperlocal climate data.
Sponsored
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.