Average Temperatures for Illinois in September
Average temperatures for September 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
| High °F | Low °F | Place | High °C | Low °C |
|---|---|---|---|---|
| 76 | 55 | Aurora | 24 | 13 |
| 75 | 55 | Chicago Botanical Garden | 24 | 13 |
| 77 | 59 | Chicago Midway Airport | 25 | 15 |
| 76 | 57 | Chicago O'Hare Airport | 24 | 14 |
| 76 | 53 | Elgin | 24 | 12 |
| 76 | 55 | Joliet | 25 | 13 |
| 75 | 52 | Rochelle | 24 | 11 |
Northern Illinois
| High °F | Low °F | Place | High °C | Low °C |
|---|---|---|---|---|
| 74 | 55 | Antioch | 23 | 13 |
| 75 | 53 | DeKalb | 24 | 12 |
| 75 | 54 | Dixon | 24 | 12 |
| 74 | 51 | Freeport | 24 | 11 |
| 78 | 54 | Moline | 26 | 12 |
| 75 | 54 | Rockford | 24 | 12 |
| 73 | 54 | Waukegan | 23 | 12 |
Central Illinois
| High °F | Low °F | Place | High °C | Low °C |
|---|---|---|---|---|
| 80 | 60 | Alton | 27 | 15 |
| 76 | 54 | Bloomington | 25 | 12 |
| 81 | 57 | Cahokia | 27 | 14 |
| 79 | 56 | Champaign | 26 | 13 |
| 81 | 57 | Charleston | 27 | 14 |
| 79 | 56 | Danville | 26 | 13 |
| 78 | 57 | Decatur | 25 | 14 |
| 78 | 55 | Kankakee | 26 | 13 |
| 76 | 54 | Ottawa | 25 | 12 |
| 78 | 56 | Peoria | 26 | 14 |
| 78 | 56 | Quincy | 26 | 13 |
| 80 | 56 | Springfield | 27 | 13 |
Southern Illinois
| High °F | Low °F | Place | High °C | Low °C |
|---|---|---|---|---|
| 83 | 57 | Belleville | 29 | 14 |
| 82 | 60 | Cairo | 28 | 15 |
| 81 | 56 | Carbondale | 27 | 13 |
| 79 | 57 | Mt Vernon | 26 | 14 |
Reference
NOAA National Centers for Environmental Information (NCEI). Climate Normals.