December weather forecast and climate
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 also a wintry month, with temperature in the range of an average high of 39.9°F (4.4°C) and an average low of 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 wintry 39.9°F (4.4°C). The average low-temperature, in Boston, is 29.7°F (-1.3°C).

Humidity

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

Rainfall

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

Snowfall

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

Ocean temperature

In Boston, in December, the average water temperature is 46.8°F (8.2°C).
Note: 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.

Daylight

December has the shortest days of the year in Boston, with an average of 9.1h of daylight.

Sunshine

The average sunshine is 4.7h.

UV index

Months with the lowest UV index in Boston are January through March, November and December, with an average maximum UV index of 2. A UV Index of 2, and less, symbolizes a minimal health vulnerability from unsafe exposure to the UV radiation for the average 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 Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes. Beware! The strength of the UV rays is increased nearly double-fold by the reflection of the snow.
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FAQ

What is the average humidity in December in Boston?

The average relative humidity in December is 76%.

What is the wettest month in Boston?

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

How many days does it rain in December in Boston?

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

How much does it snow in Boston in December?

In December, in Boston, it is snowing for 5.2 days. Throughout December, 2.83" (72mm) of snow is accumulated.

What is the water temperature in December in Boston?

In Boston, Massachusetts, in December, the average water temperature is 46.8°F (8.2°C). Swimming in 46.8°F (8.2°C) is considered dangerous. Unprotected immersion in temperatures below 50°F (10°C) causes quickly maximum intensity cold shock with hyperventilation.

What is the month with the shortest days in Boston?

With an average of 9.1h of daylight, December has the shortest days of the year in Boston, Massachusetts.

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

In December, the average length of the day in Boston is 9.1h.

How long on average sun shines in December in Boston?

The average sunshine in December in Boston is 4.7h.

What is the month 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 in Boston.

What is the UV index reading in December in Boston?

In Boston, 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 the exposure to the Sun's UV rays.

Average temperature in December
Boston, MA

Average temperature in December - Boston, MA
  • Average high temperature in December: 4.4°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 December: -1.3°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).

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Average pressure in December
Boston, MA

Average pressure in December - Boston, MA
  • Average pressure in December: 1017mbar

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

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Average wind speed in December
Boston, MA

Average wind speed in December - Boston, MA
  • Average wind speed in December: 15.1km/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).

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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: 74mm

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

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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: 72mm

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

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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

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).

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Average sea temperature in December
Boston, MA

Average sea temperature in December - Boston, MA
  • Average sea temperature in December: 8.2°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).

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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: 9.1h

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 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

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).

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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: 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).

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