NOAA NCEI Climate Normals 1991–2020
Illinois Weather by Month
Temperature, rain and the hurricane season at 134 Illinois stations, month by month.
Data: NOAA NHC HURDAT2 and NOAA SPC tornado and hail reports, through 2025 · Updated
The median station records 39.9 inches of precipitation a year; Anna 2 NNE, IL records the most, 51.1 inches, and Chicago Palwaukee Airport, IL the least, 32.3 (1.6 times as much). July is the hottest month at the median station (average high 86°F); the hottest July is at Belleville Siu Rsch, IL, 90°F. January is the coldest (average low 18°F); the coldest January nights are at Mt Carroll, IL, 11°F. Highs reach 90°F on 23 days a year at the median station and on 58 at Kaskaskia Rvr Navigation Lock, IL, the most. Snowfall is heaviest at Lake Villa 2NE, IL, 43.4 inches a year.
This page compares the 1991–2020 NOAA climate normals of 134 Illinois weather stations, each the nearest station with full normals to at least one of the 548 Illinois cities on this site that have one within 25 miles.
At the median station, May is the wettest month (4.8 inches) and February the driest (2.0). Station by station, the wettest month is May at 77, June at 40 and April at 12 of the 134, and the driest February at 83, January at 45 and August at 3. The gap between the wettest and driest station is widest in March: 3.1 inches.
Month by month across Illinois
High, low and precipitation are the median of the 134 stations; the station columns name the station with the highest average high, the lowest average low, and the most and least precipitation that month, each linked to the city page it serves. Source: NOAA NCEI U.S. Climate Normals 1991–2020.
Illinois cities and their stations
| City | Station | Miles | Hottest month high °F | Coldest month low °F | Year precip. in |
|---|---|---|---|---|---|
| Naperville | Wheaton 3 SE, IL | 6 | 86 | 17 | 40.1 |
| Joliet | Joliet Brandon Rd Dam, IL | 2 | 84 | 17 | 38.1 |
| Champaign | Champaign 3S, IL | 3 | 85 | 18 | 41.0 |
| Belleville | Belleville Siu Rsch, IL | 8 | 90 | 24 | 43.4 |
| Bolingbrook | Romeoville WFO, IL | 7 | 85 | 16 | 41.3 |
| Downers Grove | Wheaton 3 SE, IL | 4 | 86 | 17 | 40.1 |
| Oak Lawn | Chicago Midway Airport 3SW, IL | 2 | 85 | 20 | 40.9 |
| Normal | Normal 4NE, IL | 3 | 86 | 16 | 39.3 |
| Romeoville | Romeoville WFO, IL | 3 | 85 | 16 | 41.3 |
| Granite City | Alton - Melvin Price L&D, IL | 10 | 87 | 22 | 41.9 |
| Lockport | Romeoville WFO, IL | 3 | 85 | 16 | 41.3 |
| O Fallon | Belleville Siu Rsch, IL | 6 | 90 | 24 | 43.4 |
| Woodridge | Wheaton 3 SE, IL | 4 | 86 | 17 | 40.1 |
| Collinsville | Cahokia St Louis Airport, IL | 12 | 89 | 24 | 41.0 |
| La Grange | Chicago Midway Airport 3SW, IL | 6 | 85 | 20 | 40.9 |
| Oakbrook Terrace | Wheaton 3 SE, IL | 7 | 86 | 17 | 40.1 |
| Alton | Alton - Melvin Price L&D, IL | 3 | 87 | 22 | 41.9 |
| Burbank | Chicago Midway Airport 3SW, IL | <1 | 85 | 20 | 40.9 |
| Westmont | Wheaton 3 SE, IL | 5 | 86 | 17 | 40.1 |
| Lemont | Romeoville WFO, IL | 7 | 85 | 16 | 41.3 |
| Darien | Wheaton 3 SE, IL | 7 | 86 | 17 | 40.1 |
| Homer Glen | Romeoville WFO, IL | 4 | 85 | 16 | 41.3 |
| East Saint Louis | Cahokia St Louis Airport, IL | 4 | 89 | 24 | 41.0 |
| Brookfield | Chicago Midway Airport, IL | 6 | 85 | 19 | 34.7 |
| Palos Hills | Chicago Midway Airport 3SW, IL | 4 | 85 | 20 | 40.9 |
| Hinsdale | Wheaton 3 SE, IL | 8 | 86 | 17 | 40.1 |
| Crest Hill | Joliet Brandon Rd Dam, IL | 3 | 84 | 17 | 38.1 |
| Bridgeview | Chicago Midway Airport 3SW, IL | 2 | 85 | 20 | 40.9 |
| Fairview Heights | Cahokia St Louis Airport, IL | 9 | 89 | 24 | 41.0 |
| Riverside | Chicago Midway Airport, IL | 5 | 85 | 19 | 34.7 |
| Westchester | Chicago Midway Airport, IL | 8 | 85 | 19 | 34.7 |
| Troy | Belleville Siu Rsch, IL | 14 | 90 | 24 | 43.4 |
| Hickory Hills | Chicago Midway Airport 3SW, IL | 3 | 85 | 20 | 40.9 |
| Glen Carbon | Alton - Melvin Price L&D, IL | 12 | 87 | 22 | 41.9 |
| Columbia | Cahokia, IL | 9 | 89 | 22 | 42.9 |
| Justice | Chicago Midway Airport 3SW, IL | 3 | 85 | 20 | 40.9 |
| Chicago Ridge | Chicago Midway Airport 3SW, IL | 2 | 85 | 20 | 40.9 |
| Palos Heights | Chicago Midway Airport 3SW, IL | 5 | 85 | 20 | 40.9 |
| Western Springs | Chicago Midway Airport, IL | 8 | 85 | 19 | 34.7 |
| La Grange Park | Chicago Midway Airport, IL | 7 | 85 | 19 | 34.7 |
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How stations are matched to cities and what normals are: methodology · other states by month