Napa weather in September
September in Napa: hot, dry, with clean air — an excellent time to visit.
#6 of 12 months in Napa · #173 of 604 destinations to visit in September · comfort 86/100 (tier A)
Updated June 2026 · climate normals from ERA5 reanalysis
Napa climate normals — September
| Daytime high | 31°C / 88°F | 🥵 hot |
|---|---|---|
| Nighttime low | 16°C / 60°F | |
| Feels like (high) | 30°C / 86°F | |
| Rainfall | 8 mm / 0.3 in | ☀️ dry |
| Rainy days | 1 days | |
| Humidity | 63% | 💧 humid |
| Dew point | 12°C / 54°F | |
| Sunshine | 11.3 h/day | |
| Daylight | 12.4 h | |
| Wind | 15 km/h / 9 mph | |
| Air quality (US AQI) | 34 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Napa in September — FAQ
- Is September a good time to visit Napa?
- September in Napa: hot, dry, with clean air — an excellent time to visit. It ranks #6 of 12 months for Napa on SeasonMap's comfort score (86/100).
- What is the weather like in Napa in September?
- In September, Napa averages a daily high of 30.9°C and a low of 15.5°C, with about 7.8 mm of rain over roughly 0.8 rainy days.
- What is the air quality in Napa in September?
- Napa has a mean US Air Quality Index of about 34 in September.