Boston
Massachusetts, USA
Long-term weather forecast
Long-term weather forecast

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, the first month of the autumn, in Boston, is also an agreeable month, with average temperature ranging between max 72.7°F (22.6°C) and min 57.4°F (14.1°C).

Temperature

In Boston, the average high-temperature in September marginally drops, from a warm 80.4°F (26.9°C) in August, to an agreeable 72.7°F (22.6°C). In September, the average low-temperature is 57.4°F (14.1°C).

Humidity

In September, the average relative humidity is 75%.

Rainfall

The month with the least rainfall is September when the rain falls for 10 days and typically collects 1.26" (32mm) of precipitation.

Snowfall

June through September are months without snowfall.

Ocean temperature

In Boston, the average seawater temperature is 64.8°F (18.2°C).
Note: 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).

Daylight

In September, the average length of the day is 12.5h.

Sunshine

In Boston, Massachusetts, the average sunshine is 8.4h.

UV index

In September, the average daily maximum UV index in Boston is 4. A UV Index estimate of 3 to 5 represents a moderate threat to health from the exposure to the Sun's UV radiation for the average person.
Note: The daily maximum UV index of 4 in September interpret into the following advice:
Take precautions. Light skin individuals may get burned in less than 30 minutes. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun.

What is the temperature in September in Boston?

In Boston, Massachusetts, in September, the average high-temperature is 72.7°F (22.6°C), and the average low-temperature is 57.4°F (14.1°C).

What is the average humidity in September in Boston?

In September, the average relative humidity in Boston is 75%.

How many days does it rain in September in Boston?

In September, in Boston, Massachusetts, the rain falls for 10 days. Throughout September, 1.26" (32mm) of precipitation is accumulated.

What is the driest month in Boston?

September is the month with the least rainfall in Boston, Massachusetts. Rain falls for 10 days and accumulates 1.26" (32mm) of precipitation.

Does it snow in Boston in September?

In Boston, in September, it doesn't snow. In October, it regularly snows.

When it does not snow in Boston?

June through September are months without snowfall in Boston, Massachusetts.

What is the ocean temperature in September in Boston?

In September, the average ocean temperature is 64.8°F (18.2°C). For most, swimming in 64.8°F (18.2°C) is not an enjoyable activity. Furthermore, controlling your breathing becomes progressively more difficult as the water temperature decreases from 69.8°F (21°C) to 59°F (15°C).

What is the average length of the day in September in Boston?

The average length of the day in September in Boston, Massachusetts, is 12.5h.

How many hours of sunshine does Boston have in September?

In Boston, Massachusetts, the average sunshine in September is 8.4h.

How high is the UV index in September in Boston?

In September, the average daily maximum UV index in Boston, Massachusetts, is 4. A UV Index value of 3 to 5 symbolizes a medium health risk from the exposure to the Sun's UV rays.
Average temperature in September - Boston, MA
  • Average high temperature in September: 72.7°F

The warmest month (with the highest average high temperature) is July (81.7°F).
The month with the lowest average high temperature is January (34.2°F).

  • Average low temperature in September: 57.4°F

The month with the highest average low temperature is July (64.9°F).
The coldest month (with the lowest average low temperature) is January (22.6°F).

Average humidity in September - Boston, MA
  • Average humidity in September: 75%

The month with the highest relative humidity is February (77%).
The month with the lowest relative humidity is April (69%).

Average rainfall in September - Boston, MA
  • Average rainfall in September: 1.26"

Wettest months (with the highest rainfall) are March, April and December (2.91").
The driest month (with the lowest rainfall) is September (1.26").

Average rainfall days in September - Boston, MA
  • Average rainfall days in September: 10 days

The month with the highest number of rainy days is May (15.3 days).
The month with the lowest number of rainy days is January (7.9 days).

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

The month with the highest snowfall is February (4.72").
Months with the lowest snowfall are June, July, August and September (0").

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

Months with the highest number of snowfall days are January and February (7.6 days).
Months with the lowest number of snowfall days are June, July, August and September (0 days).

Average sea temperature in September - Boston, MA
  • Average sea temperature in September: 64.8°F

The best month for swimming (with the highest average sea temperature) is August (67.9°F).
The coldest month (with the lowest average sea temperature) is February (38.1°F).

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: 8.4h

The month with most sunshine is August (Average sunshine: 10.5h).
The month with least sunshine is February (Average sunshine: 4.6h).

Average UV index in September - Boston, MA
  • Average UV index in September: 4

Months with the highest UV index are June, July and August (UV index 6).
Months with the lowest UV index are January, February, March, November and December (UV index 2).