September weather forecast and climate
Boston, MA

A beautiful natural park with the George Washington Monument in Boston, Massachusetts, with a sneak view of the city skyscrapers
A beautiful natural park with the George Washington Monument in Boston, Massachusetts, with a sneak view of the city skyscrapers
September is a transitional month into autumn, and as such, has varied weather. Generally, the extreme summer heat cools down considerably, as the temperature drops to the range of 57.4°F (14.1°C) and 72.3°F (22.4°C). The nights are cool and tolerable, but the early mornings get quite chilly.
Rainfall increases, albeit minimally, to fall for eight and a half days, collecting 87.4m in the rain gauge. Expect more tourists to visit Boston since the weather becomes stable and mild, without extreme hazards like thunderstorms and heatwaves. Swimming, though, is not a regular activity, appreciative of the sea temperature dropping to 60.8°F (16°C). The lovers of cold water may take a few swims and later bask in the eight hours of daily sunshine.

What is the temperature in September in Boston?

In September, the average high-temperature is 72.3°F (22.4°C), and the average low-temperature is 57.4°F (14.1°C).

How much does it rain in Boston in September?

In September, in Boston, Massachusetts, the rain falls for 8.6 days. Throughout September, 3.4" (87.4mm) of precipitation is accumulated.

What is the sea water temperature in September in Boston?

In September, in Boston, the average sea temperature is 64.8°F (18.2°C). Swimming in 64.8°F (18.2°C) is not enjoyable for the majority. Controlling breathing becomes progressively more difficult as surface water temperature decreases below 69.8°F (21°C).
Average temperature in September - Boston, MA
  • Average high temperature in September: 22.4°C

The warmest month (with the highest average high temperature) is July (27.4°C).
The month with the lowest average high temperature is January (2.1°C).

  • Average low temperature in September: 14.1°C

The month with the highest average low temperature is July (18.6°C).
The coldest month (with the lowest average low temperature) is January (-5.4°C).

Average humidity in September - Boston, MA
  • Average humidity in September: 71.8%

The month with the highest relative humidity is September (71.8%).
The month with the lowest relative humidity is February (62%).

Average rainfall in September - Boston, MA
  • Average rainfall in September: 87.4mm

The wettest month (with the highest rainfall) is March (109.7mm).
The driest month (with the lowest rainfall) is February (82.6mm).

Average rainfall days in September - Boston, MA
  • Average rainfall days in September: 8.6 days

The month with the highest number of rainy days is May (12 days).
The month with the lowest number of rainy days is September (8.6 days).

Average snowfall in September - Boston, MA
  • Average snowfall in September: 0mm

The month with the highest snowfall is January (327.7mm).
Months with the lowest snowfall are May, June, July, August, September and October (0mm).

Average snowfall days in September - Boston, MA
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (6.7 days).
Months with the lowest number of snowfall days are May, June, July, August and September (0 days).

Average sea temperature in September - Boston, MA
  • Average sea temperature in September: 18.2°C

The best month for swimming (with the highest average sea temperature) is August (20°C).
The coldest month (with the lowest average sea temperature) is February (3.4°C).

Average daylight in September / Average sunshine in September - Boston, MA
  • Average daylight in September: 12.5h

The month with the longest days is June (Average daylight: 15.2h).
The month with shortest days is December (Average daylight: 9.1h).

  • Average sunshine in September: 7.9h

The month with most sunshine is July (Average sunshine: 9.7h).
The month with least sunshine is December (Average sunshine: 4.6h).

Average UV index in September - Boston, MA
  • Average UV index in September: 6

Months with the highest UV index are June, July and August (UV index 8).
Months with the lowest UV index are January and December (UV index 1).

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