Flagstaff weather in September
September in Flagstaff: warm, a little rain, with clean air — one of the best months to visit.
#1 of 12 months in Flagstaff · #25 of 897 destinations to visit in September · comfort 95/100 (tier S)
Updated June 2026 · climate normals from ERA5 reanalysis
Traveller notes on Flagstaff in September
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Flagstaff climate normals — September
| Daytime high | 25°C / 77°F | 🌤 warm |
|---|---|---|
| Nighttime low | 14°C / 56°F | |
| Rainfall | 50 mm / 2 in | 🌦 some rain |
| Rainy days | 8 days | |
| Humidity | 53% | 🍃 comfortable |
| Dew point | 7°C / 44°F | |
| Sunshine | 11.1 h/day | |
| Daylight | 12.4 h | |
| Wind | 15 km/h / 9 mph | |
| Air quality (US AQI) | 41 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Flagstaff in September — FAQ
- Is September a good time to visit Flagstaff?
- September in Flagstaff: warm, a little rain, with clean air — one of the best months to visit. It ranks #1 of 12 months for Flagstaff on SeasonMap's comfort score (95/100).
- What is the weather like in Flagstaff in September?
- In September, Flagstaff averages a daily high of 24.9°C and a low of 13.5°C, with about 49.8 mm of rain over roughly 7.8 rainy days.
- What is the air quality in Flagstaff in September?
- Flagstaff has a mean US Air Quality Index of about 41 in September.