Rocky Mountain National Park weather in September
September in Rocky Mountain National Park: nice, a little rain, with clean air — one of the best months to visit.
#2 of 12 months in Rocky Mountain National Park · #48 of 604 destinations to visit in September · comfort 91/100 (tier S)
Updated June 2026 · climate normals from ERA5 reanalysis
Rocky Mountain National Park climate normals — September
| Daytime high | 18°C / 65°F | 😎 nice |
|---|---|---|
| Nighttime low | 5°C / 40°F | |
| Feels like (high) | 16°C / 61°F | |
| Rainfall | 31 mm / 1.2 in | 🌦 some rain |
| Rainy days | 7 days | |
| Humidity | 58% | 🍃 comfortable |
| Dew point | 2°C / 35°F | |
| Sunshine | 11.2 h/day | |
| Daylight | 12.5 h | |
| Wind | 13 km/h / 8 mph | |
| Snowfall | 3 cm / 1.2 in | |
| Air quality (US AQI) | 40 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Rocky Mountain National Park in September — FAQ
- Is September a good time to visit Rocky Mountain National Park?
- September in Rocky Mountain National Park: nice, a little rain, with clean air — one of the best months to visit. It ranks #2 of 12 months for Rocky Mountain National Park on SeasonMap's comfort score (91/100).
- What is the weather like in Rocky Mountain National Park in September?
- In September, Rocky Mountain National Park averages a daily high of 18.4°C and a low of 4.5°C, with about 31.3 mm of rain over roughly 7.2 rainy days.
- What is the air quality in Rocky Mountain National Park in September?
- Rocky Mountain National Park has a mean US Air Quality Index of about 40 in September.
- Does it snow in Rocky Mountain National Park in September?
- Rocky Mountain National Park sees roughly 3 cm of snowfall in September.