December weather forecast
Boston, MA

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A beautiful natural park with the George Washington Monument in Boston, Massachusetts
A beautiful natural park with the George Washington Monument in Boston, Massachusetts

Weather in December

For Boston, December is synonymous with winter, and the climatic conditions validate this perception. A considerable drop in temperatures from November's mildness indicates a high of 39.9°F (4.4°C) and a low of 29.7°F (-1.3°C). This time, the city gets smothered in holiday spirit, with sparkling lights lining the streets and festive decorations adorning houses. Despite the cold weather, the warmth of Christmas and New Year's Eve celebrations bring a cheer and joviality to the overall atmosphere.

Temperature

December in Boston, Massachusetts, comes with a decrease in the average high-temperature, falling from a chilly 49.5°F (9.7°C) in November to a cold 39.9°F (4.4°C). In the month of December, the temperature generally rests at an average low of 29.7°F (-1.3°C).

Humidity

The average relative humidity in December in Boston is 76%.

Rainfall

The wettest months in Boston are March, April and December, with an average 2.91" (74mm) of rainfall.

Snowfall

Months with snowfall are January through May, October through December. In Boston, Massachusetts, in December, during 5.2 snowfall days, 2.83" (72mm) of snow is typically accumulated. In Boston, during the entire year, snow falls for 29.8 days and aggregates up to 15.75" (400mm) of snow.

Ocean temperature

In Boston, Massachusetts, in December, the average water temperature is 46.8°F (8.2°C).
Note: Dipping into 46.8°F (8.2°C) below 50°F (10°C) is possible with the right protection; absent that, anticipate cold shock and hampered breathing. Swimming momentarily at 55.4°F (13°C) can be jarring.

Daylight

December has the shortest days of the year in Boston, with an average of 9h and 6min of daylight.
On the first day of the month, sunrise is at 6:54 am and sunset at 4:12 pm. On the last day of December, sunrise is at 7:13 am and sunset at 4:21 pm EST.

Sunshine

The average sunshine in December is 4.7h.

UV index

January through March, November and December, with an average maximum UV index of 2, are months with the lowest UV index in Boston. A UV Index value of 2, and less, symbolizes a minimal health vulnerability from exposure to the Sun's UV rays for the average person.
Note: In December, the maximum UV index of 2 suggests this advice:
Sun exposure does not present considerable issues for many, yet infants, fair-skinned people, and children necessitate constant protection. The Sun's radiation is especially intense around midday; try to stay in shade during this period. To cut down UV radiation exposure by about half, sport a wide-brim hat. Caution! The reflection of snow can nearly double the intensity of the Sun's UV radiation.
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Frequently asked questions

Is December cold in Boston?

In Boston, 39.9°F (4.4°C) is the average high-temperature and 29.7°F (-1.3°C) is the average low-temperature during December. The average heat index (a.k.a. 'apparent temperature', 'real feel'), which represents the influence of relative humidity on air temperature, in July is calculated to be 86°F (30°C).

What is the average humidity in December in Boston?

In Boston, Massachusetts, the average relative humidity in December is 76%.

What is the wettest month in Boston?

The months with the most rainfall are March, April and December, with an average 2.91" (74mm) of precipitation.

How much does it rain in Boston in December?

In Boston, Massachusetts, during December, the rain falls for 10.1 days and regularly aggregates up to 2.91" (74mm) of precipitation.

How many days does it snow in December in Boston?

In Boston, Massachusetts, during December, snow falls for 5.2 days and regularly aggregates up to 2.83" (72mm) of snow.

What is the ocean temperature in December in Boston?

In Boston, the average seawater temperature in December is 46.8°F (8.2°C). Swimming in 46.8°F (8.2°C) is considered life-threatening. Even a few minutes in 55.4°F (13°C) water is uncomfortable, and swimming below 50°F (10°C) may cause total loss of breathing control and cold shock, depending on a person's physique.

What is the month with the shortest days in Boston?

The month with the shortest days in Boston is December, with an average of 9h and 6min of daylight.

How many hours of daylight does Boston have in December?

The average day length in December is 9h and 8min.

When are sunrise and sunset in December in Boston?

In December, on the first day of the month, sunrise is at 6:54 am and sunset at 4:12 pm. On the last day of the month, in Boston, sunrise is at 7:13 am and sunset at 4:21 pm EST.

How many hours of sunshine does Boston have in December?

The average sunshine duration in December in Boston is 4.7h.

When is the lowest UV index in Boston?

The months with the lowest UV index in Boston are January through March, November and December, with an average maximum UV index of 2.

What is the UV index intensity in December in Boston?

In Boston, Massachusetts, the average daily maximum UV index in December is 2. A UV Index estimate of 2, and below, represents a minimal hazard to health from exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in December
Boston, MA

Average temperature in December - Boston, MA
  • Average high temperature in December: 39.9°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 December: 29.7°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).

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Average pressure in December
Boston, MA

Average pressure in December - Boston, MA
  • Average pressure in December: 30.03"Hg

The month with the highest atmospheric pressure is November (30.06"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).

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Average wind speed in December
Boston, MA

Average wind speed in December - Boston, MA
  • Average wind speed in December: 9.4mph

The windiest month (with the highest average wind speed) is January (9.9mph).
The calmest month (with the lowest average wind speed) is August (6.2mph).

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Average humidity in December
Boston, MA

Average humidity in December - Boston, MA
  • Average humidity in December: 76%

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

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Average rainfall in December
Boston, MA

Average rainfall in December - Boston, MA
  • Average rainfall in December: 2.91"

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

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Average rainfall days in December
Boston, MA

Average rainfall days in December - Boston, MA
  • Average rainfall days in December: 10.1 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).

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Average snowfall in December
Boston, MA

Average snowfall in December - Boston, MA
  • Average snowfall in December: 2.83"

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

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Average snowfall days in December
Boston, MA

Average snowfall days in December - Boston, MA
  • Average snowfall days in December: 5.2 days

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

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Average sea temperature in December
Boston, MA

Average sea temperature in December - Boston, MA
  • Average sea temperature in December: 46.6°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).

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Average daylight in December /
Average sunshine in December
Boston, MA

Average daylight in December / Average sunshine in December - Boston, MA
  • Average daylight in December: 9h and 1min

The month with the longest days is June (Average daylight: 15h and 12min).
The month with the shortest days is December (Average daylight: 9h and 6min).

  • Average sunshine in December: 4h and 4min

The month with the most sunshine is August (Average sunshine: 10h and 30min).
The month with the least sunshine is February (Average sunshine: 4h and 36min).

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Average sunshine days in December
Boston, MA

Average sunshine days in December - Boston, MA
  • Average sunshine days in December: 16.5 days

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

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Average UV index in December
Boston, MA

Average UV index in December - Boston, MA
  • Average UV index in December: 2

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

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Average cloud cover in December
Boston, MA

Average cloud cover in December - Boston, MA
  • Average cloud cover in December: 48

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

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Average visibility in December
Boston, MA

Average visibility in December - Boston, MA
  • Average visibility in December: 6mi

The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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Boston, Massachusetts, USA

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