Boston, Massachusetts weather in September

Averages from 2021–2025 (150 days of record).

Average high: 73°F
Average low: 58°F
Rainy days: ~10 per month
Total precipitation: 5.1 in
Warmest recorded: 92°F
Coldest recorded: 47°F

Expect September days in Boston, Massachusetts to top out around 73°F and cool to about 58°F overnight, with roughly 10 days of measurable rain across the month. In recent years September has ranged from 47°F to 92°F.

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Current Boston, Massachusetts forecast → · Historical data by Open-Meteo (ERA5).