Sun Valley weather in September
September in Sun Valley: nice, a little rain, with clean air — not the best time to visit.
#10 of 12 months in Sun Valley · #603 of 604 destinations to visit in September · comfort 22/100 (tier F)
Updated June 2026 · climate normals from ERA5 reanalysis
Sun Valley climate normals — September
| Daytime high | 22°C / 71°F | 😎 nice |
|---|---|---|
| Nighttime low | 8°C / 46°F | |
| Feels like (high) | 19°C / 66°F | |
| Rainfall | 31 mm / 1.2 in | 🌦 some rain |
| Rainy days | 6 days | |
| Humidity | 52% | 🍃 comfortable |
| Dew point | 3°C / 38°F | |
| Sunshine | 11 h/day | |
| Daylight | 12.5 h | |
| Wind | 14 km/h / 9 mph | |
| Snowfall | 1.8 cm / 0.7 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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Sun Valley in September — FAQ
- Is September a good time to visit Sun Valley?
- September in Sun Valley: nice, a little rain, with clean air — not the best time to visit. It ranks #10 of 12 months for Sun Valley on SeasonMap's comfort score (22/100).
- What is the weather like in Sun Valley in September?
- In September, Sun Valley averages a daily high of 21.5°C and a low of 7.8°C, with about 30.8 mm of rain over roughly 5.8 rainy days.
- What is the air quality in Sun Valley in September?
- Sun Valley has a mean US Air Quality Index of about 40 in September.
- Does it snow in Sun Valley in September?
- Sun Valley sees roughly 1.8 cm of snowfall in September.