Weather in Boston in September 2025
- September is usually the wettest month of the year in Boston;
Average weather
Average temperature in Boston in September
The temperature in September is +24°C on average, with a range between a maximum of +34°C during the day and a minimum of +8°C at night.
The average maximum temperature goes down 23% by the end of the month, compared with the beginning of the month, from +23°C to +17°C.
Is Boston warm or cold in September?
Boston is typically mild in September.
Maximum temperatures go down compared to the previous month from +26°C to +22°C. The minimum temperature also goes down from +18°C to +15°C.
Pack a light jacket as it will be warm in the day and cool in the evenings.
Take a look at how September is compared to other months in Boston:
Water temperature in Boston in September
Water in Boston in September is Fresh. It varies from +16°C to +20°C, with an average of +18°C. This is almost similar to the air temperature, which averages +22°C.
The water temperature in September is one of the warmest of the entire year:
Can you swim in Boston in September?
Climate in Boston in September
| August | September | October | ||||
|---|---|---|---|---|---|---|
| Avg. temperature | ||||||
| +26°C | +22°C | +17°C | ||||
| Min. temperature | ||||||
| +8°C | +3°C | -3°C | ||||
| Max. temperature | ||||||
| +36°C | +35°C | +29°C | ||||
| Rainfall | ||||||
| 111 mm | 98 mm | 110 mm | ||||
| Wind | ||||||
| 3 m/s | 3 m/s | 4 m/s | ||||
| Avg. water temperature | ||||||
| +20°C | +18°C | +15°C | ||||
| Humidity | ||||||
| 70% | 72% | 70% | ||||
| Air pressure | ||||||
| 1015 HPa | 1017 HPa | 1016 HPa | ||||
| Sunny days | ||||||
| 5 | 7 | 7 | ||||
| Cloudy days | ||||||
| 10 | 10 | 11 | ||||
| Rainy days | ||||||
| 14 | 12 | 13 | ||||
| Snowy days | ||||||
| 0 | 0 | 0 | ||||
September weather is still as good as in August. It’s getting colder in September. From +26°C in the day, the average maximum temperature lowers to +22°C. As September arrives, the amount of rainfall goes down. On average, the rainfall volume decreases from 111 mm to 98 mm. Humidity rises from 70% to 72%. The average wind speed doesn’t change much during September, staying around 3 m/s. The good news is there are likely to be more sunny days in September, from 5 to 7.
October brings much the same weather, it remains good.
Wind
The average wind speed is 3 m/s getting up to 8 m/s which is a medium breeze. You can feel it, especially getting out of the water.
The average wind speed in Boston is gradually increasing during September, going from 3 m/s to 3 m/s over the course of the month.
Rain
How was the weather last September in Boston?
Climate Change over Years
The climate in Boston in September has not changed much over the last 43 years.
The average temperature was the lowest in 1992 (+14°C) and the highest in 2022 (+17°C). The driest year was 2016 with only 702 mm of rainfall, and the wettest year was 2021 with 2022 mm.
FAQ
Is September a good time to visit Boston?
Can you sunbathe in Boston in September?
Can you swim in Boston in September?
Is Boston rainy in September?
Is it sunny in Boston in September?
Other cities in USA
Monthly weather in Boston
Source of the data
For this page, we’ve looked at the typical weather in Boston, based on historical hourly weather data from January 1, 1979, to December 31, 2023.
For past dates, we show actual recorded data at the location at that time. Forecasts are based on recorded weather during that day of the year, averaged over the total years for which we have records (unless stated otherwise). The daily temperature is the highest recorded temperature in the shadow during that day.