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
The first month of the autumn, September, is still a pleasant month in Boston, Massachusetts, with temperature in the range of an average low of 57.4°F (14.1°C) and an average high of 72.7°F (22.6°C).

Temperature

In September, the average high-temperature slightly decreases, from a moderately hot 80.4°F (26.9°C) in August, to a pleasant 72.7°F (22.6°C). In September, the average low-temperature is 57.4°F (14.1°C).

Humidity

In Boston, the average relative humidity is 75%.

Rainfall

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

Snowfall

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

Ocean temperature

In Boston, the average water temperature is 64.8°F (18.2°C).
Note: For swimming, a surface water temperature of 64.8°F (18.2°C) is not enjoyable for the majority. It is not considered safe, as controlling breathing becomes progressively more difficult as water temperature decreases below 69.8°F (21°C).

Daylight

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

Sunshine

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

UV index

In Boston, the average daily maximum UV index in September is 4. A UV Index reading of 3 to 5 represents a moderate threat to health from the exposure to the Sun's UV rays for ordinary individuals.
Note: In September, the average maximum UV index of 4 translate into the following recommendations:
Take precautions - Protection against the skin and eye damage is obliged. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects.

What is the temperature in September in Boston?

In September, in Boston, Massachusetts, 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?

The average relative humidity in September in Boston is 75%.

How much does it rain in Boston in September?

In Boston, in September, it is raining for 10 days, with typically 1.26" (32mm) of accumulated precipitation.

What is the driest month in Boston?

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

Does it snow in Boston in September?

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

When it does not snow in Boston?

In Boston snow does not fall in June through September.

How cold is the water in September in Boston?

In Boston, in September, the average water temperature is 64.8°F (18.2°C). For swimming, a surface water temperature of 64.8°F (18.2°C) is not enjoyable for the majority. It is not considered safe, as controlling breathing becomes progressively more difficult as water temperature decreases below 69.8°F (21°C).

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

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

How many hours of sunshine does Boston have in September?

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

What is the UV index intensity in September in Boston?

In Boston, the average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a moderate vulnerability from unprotected exposure to the UV radiation.
Average temperature in September - Boston, MA
  • Average high temperature in September: 22.6°C

The warmest month (with the highest average high temperature) is July (27.6°C).
The month with the lowest average high temperature is January (1.2°C).

  • Average low temperature in September: 14.1°C

The month with the highest average low temperature is July (18.3°C).
The coldest month (with the lowest average low temperature) is January (-5.2°C).

Average pressure in September - Boston, MA
  • Average pressure in September: 1017.7mbar

The month with the highest atmospheric pressure is November (1018.1mbar).
The month with the lowest atmospheric pressure is June (1013.4mbar).

Average wind speed in September - Boston, MA
  • Average wind speed in September: 10.9km/h

The windiest month (with the highest average wind speed) is January (15.9km/h).
The calmest month (with the lowest average wind speed) is August (9.9km/h).

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: 32mm

The wettest months (with the highest rainfall) are March, April and December (74mm).
The driest month (with the least rainfall) is September (32mm).

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 least rainy days is January (7.9 days).

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

The month with the highest snowfall is February (120mm).
Months with the least snowfall are June, July, August and September (0mm).

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 least snowfall days are 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 the shortest days is December (Average daylight: 9.1h).

  • Average sunshine in September: 8.4h

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

Average sunshine days in September - Boston, MA
  • Average sunshine days in September: 17.7 days

The month with the most sunshine days is September (17.7 days).
The month with the least sunshine days is April (13 days).

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).

Average cloud cover in September - Boston, MA
  • Average cloud cover in September: 37

The month with the most cloud cover is March (Cloud cover 51).
The month with the least cloud cover is August (Cloud cover 32).

Average visibility in September - Boston, MA
  • Average visibility in September: 9km

Months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (9km).
Months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (9km).