Average August Temperatures for Illinois

Average temperatures for August at cities throughout Illinois are listed below.

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

The tables give the normal maximum and minimum temperatures based on weather data collected from 1991 to 2020 by the US National Centers for Environmental Information.

Chicago Area

Average August temperatures in °F
High °F	Low °F	Place	High °C	Low °C
82	63	Aurora	28	17
82	62	Chicago Botanical Garden	28	17
83	67	Chicago Midway Airport	28	19
83	65	Chicago O'Hare Airport	28	18
82	61	Elgin	28	16
82	63	Joliet	28	17
81	60	Rochelle	27	15

Northern Illinois

Average August temperatures
High °F	Low °F	Place	High °C	Low °C
81	63	Antioch	27	17
81	61	DeKalb	27	16
81	62	Dixon	27	17
81	60	Freeport	27	16
84	63	Moline	29	17
82	62	Rockford	28	17
80	61	Waukegan	27	16

Central Illinois

Normal temperatures for August
High °F	Low °F	Place	High °C	Low °C
86	67	Alton	30	20
83	61	Bloomington	28	16
88	66	Cahokia	31	19
84	64	Champaign	29	18
87	64	Charleston	30	18
84	63	Danville	29	17
84	65	Decatur	29	18
83	63	Kankakee	28	17
82	62	Ottawa	28	17
85	64	Peoria	29	18
85	65	Quincy	29	18
85	64	Springfield	30	18

Southern Illinois

Average temperatures in August
High °F	Low °F	Place	High °C	Low °C
89	65	Belleville	32	19
88	68	Cairo	31	20
87	65	Carbondale	31	18
85	65	Mt Vernon	29	18

Average Temperatures for Illinois in August

Chicago Area

Northern Illinois

Central Illinois

Southern Illinois

Reference

More Illinois Weather Information