Boston weather in September
September in Boston: nice, rainy, with clean air — an excellent time to visit.
#3 of 12 months in Boston · #190 of 604 destinations to visit in September · comfort 85/100 (tier A)
Updated June 2026 · climate normals from ERA5 reanalysis
Boston climate normals — September
| Daytime high | 23°C / 73°F | 😎 nice |
|---|---|---|
| Nighttime low | 15°C / 60°F | |
| Feels like (high) | 23°C / 73°F | |
| Rainfall | 99 mm / 3.9 in | 🌧 rainy |
| Rainy days | 9 days | |
| Humidity | 78% | 💦 very humid |
| Dew point | 14°C / 58°F | |
| Sunshine | 8.8 h/day | |
| Daylight | 12.5 h | |
| Wind | 18 km/h / 11 mph | |
| Air quality (US AQI) | 46 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Boston in September — FAQ
- Is September a good time to visit Boston?
- September in Boston: nice, rainy, with clean air — an excellent time to visit. It ranks #3 of 12 months for Boston on SeasonMap's comfort score (85/100).
- What is the weather like in Boston in September?
- In September, Boston averages a daily high of 22.9°C and a low of 15.3°C, with about 99 mm of rain over roughly 9.2 rainy days.
- What is the air quality in Boston in September?
- Boston has a mean US Air Quality Index of about 46 in September.