December 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 winter, December, is also a wintry month in Boston, Massachusetts, with average temperature ranging between max 39.9°F (4.4°C) and min 29.7°F (-1.3°C).

Temperature

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

Humidity

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, during 5.2 snowfall days, 2.83" (72mm) of snow is typically accumulated. Throughout the year, there are 29.8 snowfall days, and 15.75" (400mm) of snow is accumulated.

Ocean temperature

In Boston, Massachusetts, the average seawater 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

The month with the shortest days in Boston is December, with an average of 9.1h of daylight.

Sunshine

In December, the average sunshine in Boston 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 of 2, and less, symbolizes a minimal health vulnerability from unsafe exposure to the UV radiation for ordinary individuals.
Note: The daily maximum UV index of 2 in December interpret into the following advice:
People with sensitive skin, children, and babies should always be protected from prolonged sun exposure. 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. Caution! The reflection of snow can nearly double the intensity of the Sun's UV radiation.

What is the temperature in December in Boston?

In December, in Boston, the average high-temperature is 39.9°F (4.4°C), and the average low-temperature is 29.7°F (-1.3°C).

What is the average humidity in December in Boston?

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

How much does it rain in Boston in December?

In Boston, Massachusetts, in December, it is raining for 10.1 days, with typically 2.91" (74mm) of accumulated precipitation.

What is the rainiest month in Boston?

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 snow in December in Boston?

In Boston, in December, during 5.2 snowfall days, 2.83" (72mm) of snow is typically accumulated.

How cold is the water 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?

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

How many hours of daylight does Boston have in December?

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

How long on average sun shines in December in Boston?

The average sunshine in December is 4.7h.

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

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 December, the average daily maximum UV index in Boston, Massachusetts, is 2. A UV Index reading of 2, and below, represents a low health threat from unprotected exposure to the UV radiation.
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).

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).

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).

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%).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).