Indianapolis weather in September
September in Indianapolis: warm, a little rain, with clean air — one of the best months to visit.
#1 of 12 months in Indianapolis · #102 of 897 destinations to visit in September · comfort 92/100 (tier S)
Updated June 2026 · climate normals from ERA5 reanalysis
Traveller notes on Indianapolis in September
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Indianapolis climate normals — September
| Daytime high | 26°C / 79°F | 🌤 warm |
|---|---|---|
| Nighttime low | 17°C / 62°F | |
| Rainfall | 50 mm / 2 in | 🌦 some rain |
| Rainy days | 7 days | |
| Humidity | 70% | 💧 humid |
| Dew point | 14°C / 57°F | |
| Sunshine | 10.2 h/day | |
| Daylight | 12.4 h | |
| Wind | 15 km/h / 10 mph | |
| Air quality (US AQI) | 42 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Indianapolis in September — FAQ
- Is September a good time to visit Indianapolis?
- September in Indianapolis: warm, a little rain, with clean air — one of the best months to visit. It ranks #1 of 12 months for Indianapolis on SeasonMap's comfort score (92/100).
- What is the weather like in Indianapolis in September?
- In September, Indianapolis averages a daily high of 26.1°C and a low of 16.6°C, with about 50.2 mm of rain over roughly 6.8 rainy days.
- What is the air quality in Indianapolis in September?
- Indianapolis has a mean US Air Quality Index of about 42 in September.