Jersey County Climate
Jersey County, Illinois
Avg Annual Temp
53.4°F
Annual Precip
42.2"
Annual Snowfall
12.5"
Extreme Heat Days
28.9
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Seasonal Overview
National Comparison
Climate Profile
About Jersey County Weather
Warmer than the national median
Jersey County maintains an average annual temperature of 53.4°F, positioning it slightly above the national median for humidity and warmth. This climate represents a classic transition zone between the cooler northern states and the humid subtropics.
Above the Illinois state average
The county's 53.4°F average temperature exceeds the Illinois state average of 52.8°F. It records 42.2 inches of annual precipitation, which is slightly higher than the state-wide average of 41.7 inches.
A warmer choice than northern neighbors
Jersey County is significantly warmer than Jo Daviess County to the north, which averages only 47.4°F. While neighbors in the Chicago area face much heavier snowfall, Jersey sees a more moderate 12.5 inches annually.
Hot summers and mild winters
Summer heat is intense with 29 days per year reaching 90°F or higher. Winter remains relatively mild for the region, with an average December-to-February temperature of 30.9°F.
Prioritize cooling and rain management
Residents should invest in robust air conditioning to handle the 29 extreme heat days each year. Property owners also need reliable drainage systems to manage the 42.2 inches of annual rainfall.
Frequently Asked Questions
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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.