December weather forecast
Boston, MA

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

December, the first month of the winter in Boston, is still a cold month, with an average temperature fluctuating between 39.9°F (4.4°C) and 29.7°F (-1.3°C).

Temperature

In December, the average high-temperature decreases from a chilly 49.5°F (9.7°C) in November to a cold 39.9°F (4.4°C). The average low-temperature, in Boston, is 29.7°F (-1.3°C).

Humidity

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

Rainfall

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

Snowfall

January through May, October through December are months with snowfall. In Boston, 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, the average seawater temperature in December is 46.8°F (8.2°C).
Note: At temperatures below 50°F (10°C), swimming in a suitably protected swimsuit is feasible; otherwise, cold shock and loss of breathing control are imminent. Even a short swim, without thermal protection, at temperatures around 55.4°F (13°C) is not comfortable.

Daylight

December has the shortest days of the year in Boston, Massachusetts, with an average of 9h and 8min of daylight.
On the first day of the month, sunrise is at 6:53 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 in Boston is 4.7h.

UV index

The months with the lowest UV index are January through March, November and December, with an average maximum UV index of 2. A UV Index of 2, and less, symbolizes a low health risk from unsafe exposure to UV radiation for the ordinary person.
Note: In December, the average maximum UV index of 2 translate into the following recommendations:
Most people can stay in the Sun for up to 1 hour without burning, apart from children that always must be protected from sun exposure. 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. Caution! The reflection of snow can nearly double the intensity of the Sun's UV radiation.
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FAQ

What is the average humidity in December in Boston?

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

What is the rainiest month in Boston?

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

How many days does it rain in December in Boston?

In December, in Boston, Massachusetts, the rain falls for 10.1 days. Throughout December, 2.91" (74mm) of precipitation is accumulated.

How many days does it snow in December in Boston?

In Boston, 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, Massachusetts, in December, the average water temperature is 46.8°F (8.2°C). At temperatures below 50°F (10°C), swimming in a suitably protected swimsuit is feasible; otherwise, cold shock and loss of breathing control are imminent. Even a short swim, without thermal protection, at temperatures around 55.4°F (13°C) is not comfortable.

What is the month with the shortest days in Boston?

December has the shortest days of the year, with an average of 9h and 8min of daylight.

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

In December, the average day length is 9h and 8min.

When is the sunrise / sunset in December in Boston?

On the first day of December in Boston, sunrise is at 6:53 am and sunset at 4:12 pm. On the last day of the month, sunrise is at 7:13 am and sunset at 4:21 pm EST.

How long on average sun shines in December in Boston?

In December, the average sunshine duration is 4.7h.

What are the months with the lowest UV index in Boston?

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

What is the UV index reading in December in Boston?

The average daily maximum UV index in December is 2. A UV Index of 2, and less, symbolizes a low health threat from unsafe exposure to Sun's UV rays.

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"

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

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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 8min

The month with the longest days is June (Average daylight: 15h and 14min).
The month with the shortest days is December (Average daylight: 9h and 8min).

  • Average sunshine in December: 4.7h

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

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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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