Yellowstone National Park weather in September
September in Yellowstone National Park: cool, a little rain, with clean air — an excellent time to visit.
#3 of 12 months in Yellowstone National Park · #187 of 604 destinations to visit in September · comfort 86/100 (tier A)
Updated June 2026 · climate normals from ERA5 reanalysis
Yellowstone National Park climate normals — September
| Daytime high | 17°C / 63°F | 🙂 cool |
|---|---|---|
| Nighttime low | 5°C / 41°F | |
| Feels like (high) | 13°C / 55°F | |
| Rainfall | 66 mm / 2.6 in | 🌦 some rain |
| Rainy days | 9 days | |
| Humidity | 62% | 💧 humid |
| Dew point | 2°C / 36°F | |
| Sunshine | 10.5 h/day | |
| Daylight | 12.5 h | |
| Wind | 18 km/h / 11 mph | |
| Snowfall | 9.9 cm / 3.9 in | |
| 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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Yellowstone National Park in September — FAQ
- Is September a good time to visit Yellowstone National Park?
- September in Yellowstone National Park: cool, a little rain, with clean air — an excellent time to visit. It ranks #3 of 12 months for Yellowstone National Park on SeasonMap's comfort score (86/100).
- What is the weather like in Yellowstone National Park in September?
- In September, Yellowstone National Park averages a daily high of 17.1°C and a low of 4.8°C, with about 66.3 mm of rain over roughly 9 rainy days.
- What is the air quality in Yellowstone National Park in September?
- Yellowstone National Park has a mean US Air Quality Index of about 43 in September.
- Does it snow in Yellowstone National Park in September?
- Yellowstone National Park sees roughly 9.9 cm of snowfall in September.