December weather forecast
Chelmsford, MA

Weather in December

December, the first month of the winter in Chelmsford, is also a wintry month, with an average temperature fluctuating between 27.3°F (-2.6°C) and 37.9°F (3.3°C).

Temperature

In December, the average high-temperature decreases from a frosty 48.2°F (9°C) in November to a cold 37.9°F (3.3°C). The average low-temperature, is 27.3°F (-2.6°C).

Humidity

In Chelmsford, the average relative humidity in December is 77%.

Rainfall

The month with the most rainfall is December, when the rain falls for 10.9 days and typically aggregates up to 2.87" (73mm) of precipitation.

Snowfall

Months with snowfall in Chelmsford are January through May, October through December. In December, in Chelmsford, it is snowing for 5.6 days. Throughout December, 4.41" (112mm) of snow is accumulated. Throughout the year, there are 32.6 snowfall days, and 21.61" (549mm) of snow is accumulated.

Daylight

The month with the shortest days in Chelmsford is December, with an average of 9h and 7min of daylight.
On the first day of the month, sunrise is at 6:55 am and sunset at 4:13 pm. On the last day of December, sunrise is at 7:15 am and sunset at 4:21 pm EST.

Sunshine

In December, the average sunshine in Chelmsford is 4.9h.

UV index

January through March, November and December, with an average maximum UV index of 2, are months with the lowest UV index in Chelmsford. A UV Index value of 2, and less, symbolizes a low threat to health from unsafe exposure to UV radiation for average individuals.
Note: The average daily UV index of 2 in December transform into the following instructions:
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 the 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. 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 temperature in December in Chelmsford?

The average high-temperature, in December, in Chelmsford, is 37.9°F (3.3°C), while the average low-temperature is 27.3°F (-2.6°C). The average heat index (a.k.a. 'apparent temperature', 'real feel'), which represents the influence of relative humidity on air temperature, in August is calculated to be 84.2°F (29°C).

What is the average humidity in December in Chelmsford?

In December, the average relative humidity is 77%.

What is the rainiest month in Chelmsford?

The month with the most rainfall in Chelmsford, Massachusetts, is December, when the rain falls for 10.9 days and typically aggregates up to 2.87" (73mm) of precipitation.

How many days does it rain in December in Chelmsford?

In December, the rain falls for 10.9 days. Throughout December, 2.87" (73mm) of precipitation is accumulated.

How much does it snow in Chelmsford in December?

In Chelmsford, Massachusetts, in December, snow falls for 5.6 days, with typically accumulated 4.41" (112mm) of snow.

What is the month with the shortest days in Chelmsford?

December has the shortest days of the year, with an average of 9h and 7min of daylight.

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

In Chelmsford, the average day length in December is 9h and 7min.

When are sunrise and sunset in December in Chelmsford?

In December, on the first day of the month, sunrise is at 6:55 am and sunset at 4:13 pm. On the last day of the month, in Chelmsford, Massachusetts, sunrise is at 7:15 am and sunset at 4:21 pm EST.

How long on average sun shines in December in Chelmsford?

The average sunshine duration in December is 4.9h.

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

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

What is the UV index reading in December in Chelmsford?

In Chelmsford, the average daily maximum UV index in December is 2. A UV Index of 2, and less, symbolizes a minimal health vulnerability 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
Chelmsford, MA

Average temperature in December - Chelmsford, MA
  • Average high temperature in December: 37.9°F

The warmest month (with the highest average high temperature) is July (82.2°F).
The month with the lowest average high temperature is January (32.5°F).

  • Average low temperature in December: 27.3°F

The month with the highest average low temperature is July (63.1°F).
The coldest month (with the lowest average low temperature) is January (19.9°F).

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Average pressure in December
Chelmsford, MA

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

The month with the highest atmospheric pressure is November (30.07"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).

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Average wind speed in December
Chelmsford, MA

Average wind speed in December - Chelmsford, MA
  • Average wind speed in December: 8.3mph

The windiest month (with the highest average wind speed) is January (8.8mph).
The calmest months (with the lowest average wind speed) are July and August (5.5mph).

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Average humidity in December
Chelmsford, MA

Average humidity in December - Chelmsford, MA
  • Average humidity in December: 77%

The month with the highest relative humidity is February (80%).
The month with the lowest relative humidity is April (70%).

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Average rainfall in December
Chelmsford, MA

Average rainfall in December - Chelmsford, MA
  • Average rainfall in December: 2.87"

The wettest month (with the highest rainfall) is December (2.87").
The driest month (with the least rainfall) is September (1.46").

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Average rainfall days in December
Chelmsford, MA

Average rainfall days in December - Chelmsford, MA
  • Average rainfall days in December: 10.9 days

The month with the highest number of rainy days is May (15.6 days).
The month with the least rainy days is February (6.9 days).

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Average snowfall in December
Chelmsford, MA

Average snowfall in December - Chelmsford, MA
  • Average snowfall in December: 4.41"

The month with the highest snowfall is February (5.98").
The months with the least snowfall are June, July, August and September (0").

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Average snowfall days in December
Chelmsford, MA

Average snowfall days in December - Chelmsford, MA
  • Average snowfall days in December: 5.6 days

The month with the highest number of snowfall days is February (8.3 days).
The months with the least snowfall days are June, July, August and September (0 days).

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

Average daylight in December / Average sunshine in December - Chelmsford, MA
  • Average daylight in December: 9h and 7min

The month with the longest days is June (Average daylight: 15h and 16min).
The month with the shortest days is December (Average daylight: 9h and 7min).

  • Average sunshine in December: 4h and 54min

The month with the most sunshine is August (Average sunshine: 10h and 36min).
The month with the least sunshine is February (Average sunshine: 4h and 42min).

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Average sunshine days in December
Chelmsford, MA

Average sunshine days in December - Chelmsford, MA
  • Average sunshine days in December: 16.6 days

The month with the most sunshine days is November (17.4 days).
The month with the least sunshine days is May (13.6 days).

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Average UV index in December
Chelmsford, MA

Average UV index in December - Chelmsford, 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
Chelmsford, MA

Average cloud cover in December - Chelmsford, MA
  • Average cloud cover in December: 46

The month with the most cloud cover is March (Cloud cover 49).
The month with the least cloud cover is August (Cloud cover 31).

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Average visibility in December
Chelmsford, MA

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

The months with the highest visibility are January, March, April, May, June, July, August, September, October, November and December (6mi).
The month with the lowest visibility is February (5mi).

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