McHenry County Climate
McHenry County, Illinois
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
48.6°F
Annual Precip
38.4"
Annual Snowfall
33.1"
Extreme Heat Days
16
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
5b
Minimum winter temperature range for plant survival
2,896
Supports most vegetables & fruits
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: McHenry County
Climate Verdict
McHenry County has a cool, averaging 48.6°F annually, moderate rainfall of 38.4 inches per year, rare extreme heat with only 16.133333333333333 days above 90°F annually, moderate snowfall of 33.1 inches annually. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are very cold — January averages 21.8°F. summers are warm — July averages 72.9°F. Residents experience a substantial 51°F difference between winter and summer.
Outdoor & Gardening Guidance
Growing season and gardening data is currently limited for McHenry County. Check the USDA Plant Hardiness Zone Map and local extension office for specific guidance.
Regional Context
McHenry County is 4.2°F cooler than the Illinois statewide average of 52.8°F, it is somewhat drier than average for Illinois.
Climate Profile
About McHenry County Weather
Chilly Northern Climate and High Snow
McHenry County is notably cooler than the national average, with a mean temperature of 48.6°F. It serves as a classic example of a cold-winter humid continental climate.
One of the Coldest Illinois Counties
The average of 48.6°F is significantly lower than the Illinois state average of 52.8°F. McHenry ranks as one of the state's most northern and coldest regions.
The Snow Capital of the Region
With 33.1 inches of snow annually, McHenry receives over ten times more snowfall than southern Massac County. It also has the fewest extreme heat days in the group at just 16.
Long Winters and Mild Summers
Winter dominates here with a frigid December-February average of 24.8°F and heavy snow accumulation. Summers are pleasant and mild, with July averages peaking at only 72.9°F.
Invest in Heavy Winter Equipment
A high-quality snow blower is essential to manage the 33.1 inches of annual snowfall. Homeowners should also prioritize high-efficiency heating systems for the long, 21.8°F January nights.
Frequently Asked Questions
What is the average temperature in McHenry County?
How much rain does McHenry County get?
Does it snow in McHenry County?
How hot does McHenry County get in summer?
How cold are winters in McHenry County?
Track your own weather in McHenry County
Ambient Weather personal weather stations give you hyperlocal climate data.
Sponsored
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.