Illinois Climate Data
NOAA 30-year climate normals for all 102 counties.
State Avg Temp
52.8°F
Hottest County
Union County
58.5°F avg
Coldest County
Jo Daviess County
47.4°F avg
Wettest County
Union County
51.1" precip
All Illinois Counties
Adams County
52.9°F avg
Alexander County
58.1°F avg
Bond County
Data pending
Boone County
Data pending
Brown County
Data pending
Bureau County
49.5°F avg
Calhoun County
Data pending
Carroll County
48.5°F avg
Cass County
Data pending
Champaign County
52.1°F avg
Christian County
53.6°F avg
Clark County
54.1°F avg
Clay County
55.5°F avg
Clinton County
55.7°F avg
Coles County
54.0°F avg
Cook County
50.3°F avg
Crawford County
54.6°F avg
Cumberland County
Data pending
De Witt County
Data pending
DeKalb County
48.2°F avg
Douglas County
52.4°F avg
DuPage County
50.3°F avg
Edgar County
51.4°F avg
Edwards County
56.4°F avg
Effingham County
Data pending
Fayette County
53.8°F avg
Ford County
51.0°F avg
Franklin County
56.1°F avg
Fulton County
49.3°F avg
Gallatin County
Data pending
Greene County
52.9°F avg
Grundy County
51.0°F avg
Hamilton County
55.4°F avg
Hancock County
51.8°F avg
Hardin County
54.8°F avg
Henderson County
51.9°F avg
Henry County
50.0°F avg
Iroquois County
50.8°F avg
Jackson County
56.2°F avg
Jasper County
53.6°F avg
Jefferson County
54.5°F avg
Jersey County
53.4°F avg
Jo Daviess County
47.4°F avg
Johnson County
Data pending
Kane County
49.5°F avg
Kankakee County
51.2°F avg
Kendall County
Data pending
Knox County
49.9°F avg
Lake County
48.4°F avg
LaSalle County
49.8°F avg
Lawrence County
55.3°F avg
Lee County
48.5°F avg
Livingston County
50.9°F avg
Logan County
52.2°F avg
Macon County
53.0°F avg
Macoupin County
54.1°F avg
Madison County
55.7°F avg
Marion County
54.8°F avg
Marshall County
52.6°F avg
Mason County
52.1°F avg
Massac County
57.3°F avg
McDonough County
51.5°F avg
McHenry County
48.6°F avg
McLean County
50.6°F avg
Menard County
52.1°F avg
Mercer County
50.6°F avg
Monroe County
Data pending
Montgomery County
55.5°F avg
Morgan County
52.8°F avg
Moultrie County
53.0°F avg
Ogle County
48.6°F avg
Peoria County
51.8°F avg
Perry County
56.0°F avg
Piatt County
Data pending
Pike County
53.5°F avg
Pope County
57.2°F avg
Pulaski County
57.9°F avg
Putnam County
51.0°F avg
Randolph County
55.8°F avg
Richland County
54.2°F avg
Rock Island County
50.6°F avg
Saline County
57.3°F avg
Sangamon County
53.5°F avg
Schuyler County
51.7°F avg
Scott County
52.9°F avg
Shelby County
53.3°F avg
St. Clair County
56.8°F avg
Stark County
Data pending
Stephenson County
47.7°F avg
Tazewell County
Data pending
Union County
58.5°F avg
Vermilion County
52.3°F avg
Wabash County
56.4°F avg
Warren County
50.3°F avg
Washington County
55.1°F avg
Wayne County
57.1°F avg
White County
55.0°F avg
Whiteside County
49.1°F avg
Will County
50.6°F avg
Williamson County
Data pending
Winnebago County
49.4°F avg
Woodford County
51.6°F avg
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.