Average Rainfall for Illinois in August





The tables below give monthly averages for rainfall during August at cities in Illinois.

Each place has a total for the amount of precipitation it usually receives this month. There is also a count of the number of days with wet weather, when precipitation amounts to 0.01 inches (0.25 millimetres) or more.

The rainfall totals are averages based on weather data collected from 1991 to 2020 for the US National Centers for Environmental Information.

You can jump to a separate table for each region of the state: Chicago Area, Northern Illinois, Central Illinois and Southern Illinois.

Chicago Area

Average monthly precipitation in August
Days Place Inches Milli­metres
9 Aurora 3.9 98
10 Chicago Botanical Garden 4.2 106
9 Chicago Midway Airport 4.1 104
9 Chicago O'Hare Airport 4.3 108
10 Elgin 4.3 110
9 Joliet 4.0 101
9 Rochelle 3.9 100

Northern Illinois

August averages for total rainfall
Days Place Inches Milli­metres
9 DeKalb 4.1 103
8 Dixon 4.2 106
10 Freeport 4.2 107
9 Moline 4.0 101
9 Rockford 4.2 106
13 Waukegan 3.6 91

Central Illinois

Average amount of rain in August
Days Place Inches Milli­metres
7 Alton 3.3 84
8 Bloomington 3.8 95
8 Cahokia 3.1 78
9 Champaign 3.5 90
8 Charleston 2.9 75
9 Danville 3.3 84
7 Decatur 3.5 89
9 Kankakee 3.9 98
9 Ottawa 3.7 94
8 Peoria 3.3 84
8 Quincy 3.9 100
8 Springfield 3.4 86

Southern Illinois

Precipitation totals for August
Days Place Inches Milli­metres
7 Belleville 3.9 100
9 Carbondale 3.2 80
8 Mt Vernon 3.3 85
Reference

NOAA National Centers for Environmental Information (NCEI). Climate Normals.

Illinois Precipitation
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