Indiana Dunes National Park weather in September
September in Indiana Dunes National Park: warm, rainy, with clean air — one of the best months to visit.
#2 of 12 months in Indiana Dunes National Park · #220 of 604 destinations to visit in September · comfort 84/100 (tier A)
Updated June 2026 · climate normals from ERA5 reanalysis
Indiana Dunes National Park climate normals — September
| Daytime high | 23°C / 73°F | 🌤 warm |
|---|---|---|
| Nighttime low | 18°C / 64°F | |
| Feels like (high) | 24°C / 75°F | |
| Rainfall | 80 mm / 3.2 in | 🌧 rainy |
| Rainy days | 9 days | |
| Humidity | 75% | 💦 very humid |
| Dew point | 15°C / 59°F | |
| Sunshine | 9.6 h/day | |
| Daylight | 12.5 h | |
| Wind | 18 km/h / 11 mph | |
| Air quality (US AQI) | 43 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Indiana Dunes National Park in September — FAQ
- Is September a good time to visit Indiana Dunes National Park?
- September in Indiana Dunes National Park: warm, rainy, with clean air — one of the best months to visit. It ranks #2 of 12 months for Indiana Dunes National Park on SeasonMap's comfort score (84/100).
- What is the weather like in Indiana Dunes National Park in September?
- In September, Indiana Dunes National Park averages a daily high of 22.9°C and a low of 17.7°C, with about 80.1 mm of rain over roughly 9.2 rainy days.
- What is the air quality in Indiana Dunes National Park in September?
- Indiana Dunes National Park has a mean US Air Quality Index of about 43 in September.