Gateway Arch National Park weather in September
September in Gateway Arch National Park: hot, a little rain, with clean air — an excellent time to visit.
#3 of 12 months in Gateway Arch National Park · #242 of 604 destinations to visit in September · comfort 83/100 (tier A)
Updated June 2026 · climate normals from ERA5 reanalysis
Gateway Arch National Park climate normals — September
| Daytime high | 28°C / 82°F | 🥵 hot |
|---|---|---|
| Nighttime low | 18°C / 64°F | |
| Feels like (high) | 30°C / 86°F | |
| Rainfall | 49 mm / 1.9 in | 🌦 some rain |
| Rainy days | 6 days | |
| Humidity | 67% | 💧 humid |
| Dew point | 15°C / 59°F | |
| Sunshine | 10.5 h/day | |
| Daylight | 12.4 h | |
| Wind | 14 km/h / 9 mph | |
| Air quality (US AQI) | 50 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Where is Gateway Arch National Park?
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Gateway Arch National Park in September — FAQ
- Is September a good time to visit Gateway Arch National Park?
- September in Gateway Arch National Park: hot, a little rain, with clean air — an excellent time to visit. It ranks #3 of 12 months for Gateway Arch National Park on SeasonMap's comfort score (83/100).
- What is the weather like in Gateway Arch National Park in September?
- In September, Gateway Arch National Park averages a daily high of 27.9°C and a low of 17.9°C, with about 48.8 mm of rain over roughly 6.2 rainy days.
- What is the air quality in Gateway Arch National Park in September?
- Gateway Arch National Park has a mean US Air Quality Index of about 50 in September.