Illinois weather in September: Statewide normals and every place, NOAA 1991-2020
In September, Illinois's statewide normal high is 78°F and normal low 55°F; normal highs run from 72°F in Barrington to 84°F in Anna (NOAA 1991-2020 normals).
- Statewide normal high
- 78°FSeptember, 1991-2020
- Statewide normal low
- 55°FSeptember, 1991-2020
- Statewide normal precipitation
- 3.35 inSeptember
- Warmest place
- 84°Fnormal high, Anna
- Coolest place
- 72°Fnormal high, Barrington
Where is Illinois warmest and wettest in September?
Anna has the warmest September afternoons (84°F) and Barrington the coolest (72°F). Stockton gets the most precipitation (4.22 in) and Sullivan the least (2.71 in).
Statewide, September averaged 69.6°F in 2021, 67.0°F in 2022, 68.3°F in 2023, 68.7°F in 2024, 69.2°F in 2025, against a 1991-2020 normal of 66.8°F.
| Place | High | Low | Precip. | Snow |
|---|---|---|---|---|
| Chicago | 76°F | 57°F | 3.19 | 0.0 |
| Aurora | 76°F | 55°F | 3.37 | 0.0 |
| Joliet | 76°F | 55°F | 3.17 | 0.0 |
| Rockford | 75°F | 54°F | 3.62 | 0.0 |
| Elgin | 76°F | 53°F | 3.53 | 0.0 |
| Springfield | 80°F | 56°F | 2.88 | 0.0 |
| Peoria | 78°F | 56°F | 3.48 | 0.0 |
| Champaign | 79°F | 55°F | 3.05 | – |
| Waukegan | 74°F | 54°F | – | – |
| Bloomington | 76°F | 54°F | 3.15 | – |
| Decatur | 79°F | 55°F | 2.98 | – |
| Wheaton | 78°F | 54°F | 3.30 | 0.0 |
| Normal | 79°F | 53°F | 3.22 | 0.0 |
| Moline | 78°F | 54°F | 3.32 | 0.0 |
| Crystal Lake | 74°F | 52°F | 3.54 | 0.0 |
| Romeoville | 76°F | 55°F | 3.31 | 0.0 |
| Belleville | 83°F | 57°F | 3.35 | 0.0 |
| DeKalb | 75°F | 53°F | 3.32 | 0.0 |
| Quincy | 78°F | 56°F | 3.09 | – |
| Streamwood | 78°F | 51°F | 3.58 | 0.0 |
| Wheeling | 75°F | 56°F | 3.04 | – |
| Rock Island | 77°F | 55°F | 3.31 | – |
| Mundelein | 74°F | 53°F | 3.38 | 0.0 |
| Galesburg | 76°F | 55°F | 3.85 | 0.0 |
| Burbank | 77°F | 59°F | 3.33 | 0.0 |
| Danville | 79°F | 56°F | 3.26 | – |
| West Chicago | 76°F | 54°F | 3.00 | – |
| Alton | 80°F | 60°F | 3.38 | – |
| Lisle | 76°F | 52°F | 3.36 | – |
| Kankakee | 78°F | 55°F | 3.56 | 0.0 |
| Freeport | 74°F | 51°F | 4.11 | 0.0 |
| Carbondale | 81°F | 56°F | 2.85 | – |
| Park Forest | 76°F | 55°F | 3.44 | 0.0 |
| Ottawa | 76°F | 54°F | 3.23 | 0.0 |
| Jacksonville | 80°F | 55°F | 3.78 | – |
| Charleston | 81°F | 57°F | 3.15 | 0.0 |
| Cahokia Heights | 81°F | 57°F | 3.36 | – |
| Mattoon | 79°F | 56°F | 2.85 | – |
| Dixon | 75°F | 54°F | 3.69 | 0.0 |
| Antioch | 74°F | 55°F | – | – |
| Morris | 77°F | 55°F | 3.55 | 0.0 |
| Channahon | 77°F | 56°F | 3.25 | 0.0 |
| Mount Vernon | 79°F | 57°F | 3.37 | 0.0 |
| Lincoln | 79°F | 53°F | 3.30 | 0.0 |
| Effingham | 81°F | 56°F | 2.89 | 0.0 |
| Streator | 78°F | 55°F | 3.56 | 0.0 |
| Rantoul | 81°F | 54°F | 3.28 | – |
| Kewanee | 77°F | 52°F | 3.68 | 0.0 |
| Pontiac | 78°F | 56°F | 3.39 | 0.0 |
| Barrington | 72°F | 54°F | 3.65 | 0.0 |
| Peru | 77°F | 53°F | 3.41 | 0.0 |
| Rochelle | 75°F | 52°F | 3.26 | – |
| Lake Villa | 73°F | 54°F | 3.36 | 0.0 |
| Monmouth | 77°F | 54°F | 3.70 | 0.0 |
| Olney | 80°F | 56°F | 3.31 | 0.0 |
| Jerseyville | 79°F | 55°F | 3.44 | 0.0 |
| Paris | 78°F | 54°F | 2.94 | 0.0 |
| Harrisburg | 82°F | 57°F | 3.10 | – |
| Marengo | 75°F | 52°F | 3.68 | 0.0 |
| Princeton | 76°F | 53°F | 3.90 | 0.0 |
| Vandalia | 80°F | 56°F | 3.07 | – |
| Robinson | 81°F | 56°F | 3.66 | – |
| Salem | 80°F | 57°F | 3.54 | 0.0 |
| Mount Carmel | 81°F | 59°F | 3.51 | 0.0 |
| Benton | 81°F | 58°F | – | – |
| Geneseo | 77°F | 55°F | 3.57 | 0.0 |
| Hillsboro | 82°F | 57°F | 3.30 | – |
| Du Quoin | 80°F | 57°F | 3.40 | 0.0 |
| Carlinville | 79°F | 55°F | 3.32 | 0.0 |
| Pana | 81°F | 55°F | 3.25 | 0.0 |
| Fairfield | 83°F | 58°F | 2.90 | – |
| Marseilles | 77°F | 53°F | 3.46 | 0.0 |
| Hoopeston | 79°F | 55°F | 3.36 | 0.0 |
| Carmi | 81°F | 55°F | 3.22 | 0.0 |
| Tuscola | 79°F | 55°F | 3.07 | 0.0 |
| Flora | 82°F | 55°F | 3.34 | 0.0 |
| Shelbyville | 80°F | 57°F | 3.06 | – |
| Watseka | 79°F | 52°F | 3.19 | 0.0 |
| Paxton | 79°F | 52°F | 3.00 | 0.0 |
| Lawrenceville | 82°F | 57°F | 2.94 | – |
| Sullivan | 80°F | 55°F | 2.71 | 0.0 |
| Anna | 84°F | 59°F | 3.49 | 0.0 |
| Pittsfield | 80°F | 55°F | 3.61 | 0.0 |
| Sparta | 81°F | 55°F | 3.03 | 0.0 |
| Dwight | 77°F | 51°F | 3.25 | 0.0 |
| Morrison | 75°F | 51°F | 3.35 | 0.0 |
| Fulton | 76°F | 55°F | 3.66 | – |
| Aledo | 77°F | 53°F | 3.73 | 0.0 |
| Gibson City | 78°F | 53°F | 3.20 | 0.0 |
| Carlyle | 81°F | 58°F | 3.65 | – |
| Galena | 74°F | 51°F | 3.86 | 0.0 |
| Virden | 80°F | 58°F | 3.42 | 0.0 |
| Nashville | 80°F | 58°F | 3.54 | 0.0 |
| Rushville | 77°F | 55°F | 3.92 | – |
| Knoxville | 76°F | 54°F | 4.18 | 0.0 |
| Havana | 80°F | 54°F | 3.26 | 0.0 |
| Newton | 80°F | 57°F | 3.26 | 0.0 |
| McLeansboro | 82°F | 55°F | 3.50 | 0.0 |
| Galva | 77°F | 52°F | 3.97 | – |
| Casey | 81°F | 55°F | 3.07 | 0.0 |
| Polo | 77°F | 51°F | 3.59 | – |
| White Hall | 79°F | 55°F | 2.99 | 0.0 |
| Petersburg | 79°F | 55°F | 3.12 | 0.0 |
| Mason City | 79°F | 54°F | 3.55 | 0.0 |
| Athens | 78°F | 54°F | 3.15 | – |
| Minonk | 79°F | 54°F | 3.87 | 0.0 |
| Albion | 82°F | 60°F | – | – |
| Lacon | 80°F | 55°F | 3.30 | 0.0 |
| Princeville | 78°F | 52°F | 3.86 | 0.0 |
| Chenoa | 77°F | 53°F | 3.13 | 0.0 |
| Stockton | 74°F | 51°F | 4.22 | 0.0 |
| Cairo | 82°F | 60°F | 3.51 | – |
| Winchester | 80°F | 54°F | 3.03 | – |
| Grayville | 82°F | 57°F | 3.72 | 0.0 |
| Mount Carroll | 77°F | 50°F | 3.71 | 0.0 |
| Neoga | 81°F | 54°F | 2.93 | – |
| Walnut | 76°F | 53°F | 3.40 | 0.0 |
| Palestine | 80°F | 56°F | 3.58 | 0.0 |
| La Harpe | 77°F | 54°F | 3.83 | – |
| Windsor | 78°F | 55°F | 2.97 | 0.0 |
| Morrisonville | 81°F | 56°F | 3.53 | 0.0 |
| Rosiclare | 80°F | 55°F | 3.24 | 0.0 |
| Ramsey | 79°F | 54°F | 3.16 | 0.0 |
| Shabbona | 74°F | 50°F | 3.42 | – |
| Paw Paw | 75°F | 52°F | 3.58 | 0.0 |
| Hennepin | 77°F | 55°F | 3.45 | – |
| Piper City | 80°F | 52°F | 2.86 | 0.0 |
| Ogden | 78°F | 56°F | 3.35 | 0.0 |
| Brookport | 82°F | 59°F | 3.49 | 0.0 |
| Elizabeth | 75°F | 50°F | 3.85 | 0.0 |
| Brownstown | 80°F | 56°F | 3.38 | – |
| Avon | 77°F | 51°F | 3.65 | 0.0 |
| Golden | 79°F | 54°F | – | – |
| New Boston | 77°F | 55°F | 3.34 | – |
| Congerville | 80°F | 55°F | 3.21 | 0.0 |
| Sidell | 78°F | 54°F | 2.73 | 0.0 |
| Altona | 76°F | 52°F | 3.81 | – |
| Prairie City | 78°F | 55°F | 3.77 | 0.0 |
| Perry | 80°F | 54°F | 3.59 | 0.0 |
| Compton | 75°F | 51°F | – | – |
| Gladstone | 78°F | 56°F | 3.62 | 0.0 |
| Bentley | 79°F | 56°F | 3.67 | 0.0 |
| Kaskaskia | 81°F | 58°F | 2.94 | 0.0 |
| Illinois City | 77°F | 55°F | 3.57 | – |
| Cahokia | 80°F | 59°F | 3.35 | 0.0 |
| Chicago Aurora Municipal Airport | 76°F | 52°F | 3.01 | – |
| Chicago Botanic Garden | 75°F | 55°F | 3.56 | 0.0 |
| Chicago Midway Airport | 76°F | 59°F | 2.77 | – |
| Chicago Waukegan Regional Airport | 73°F | 54°F | 3.57 | – |
| Dixon Springs Agricultural Center | 82°F | 58°F | 3.79 | 0.0 |
| Grand Chain Dam 53 | 83°F | 60°F | 3.35 | 0.0 |
| Iuka (12 mi SW) | 81°F | 56°F | 3.29 | 0.0 |
| Little Red School House | 80°F | 55°F | 3.45 | – |
| McHenry W.G. Stratton Lock and Dam | 76°F | 51°F | 3.61 | 0.0 |
| Rend Lake Dam | 81°F | 58°F | 3.22 | – |
| Smithland Lock and Dam | 81°F | 60°F | 3.57 | 0.0 |
Source: NOAA NCEI nClimDiv statewide normals; NOAA NCEI 1991-2020 monthly normals for each station.