Chicago weather in September
September in Chicago: warm, rainy, with clean air — one of the best months to visit.
#1 of 12 months in Chicago · #111 of 604 destinations to visit in September · comfort 88/100 (tier A)
Updated June 2026 · climate normals from ERA5 reanalysis
Chicago climate normals — September
| Daytime high | 24°C / 74°F | 🌤 warm |
|---|---|---|
| Nighttime low | 17°C / 62°F | |
| Feels like (high) | 24°C / 75°F | |
| Rainfall | 89 mm / 3.5 in | 🌧 rainy |
| Rainy days | 11 days | |
| Humidity | 74% | 💧 humid |
| Dew point | 15°C / 58°F | |
| Sunshine | 9.3 h/day | |
| Daylight | 12.5 h | |
| Wind | 19 km/h / 12 mph | |
| Air quality (US AQI) | 45 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Chicago in September — FAQ
- Is September a good time to visit Chicago?
- September in Chicago: warm, rainy, with clean air — one of the best months to visit. It ranks #1 of 12 months for Chicago on SeasonMap's comfort score (88/100).
- What is the weather like in Chicago in September?
- In September, Chicago averages a daily high of 23.6°C and a low of 16.8°C, with about 89.1 mm of rain over roughly 10.8 rainy days.
- What is the air quality in Chicago in September?
- Chicago has a mean US Air Quality Index of about 45 in September.