Contents
- Weather in December
- Frequently asked questions
- Average temperature in December
- Average pressure in December
- Average wind speed in December
- Average humidity in December
- Average rainfall in December
- Average rainfall days in December
- Average snowfall in December
- Average snowfall days in December
- Average daylight in December
- Average sunshine in December
- Average sunshine days in December
- Average UV index in December
- Average cloud cover in December
- Average visibility in December
Weather in December
Temperature
A decrease in the average high-temperature is observed during December, shifting from a chilly 48.2°F (9°C) in November to a wintry 37.9°F (3.3°C). In Chelmsford, the December nights cool down to an average low of 27.3°F (-2.6°C).Humidity
In Chelmsford, the average relative humidity in December is 77%.Rainfall
December is the month with the most rainfall. Rain falls for 10.9 days and accumulates 2.87" (73mm) of precipitation.Snowfall
Months with snowfall are January through May, October through December. In Chelmsford, in December, during 5.6 snowfall days, 4.41" (112mm) of snow is typically accumulated. In Chelmsford, during the entire year, snow falls for 32.6 days and aggregates up to 21.61" (549mm) of snow.Daylight
December has the shortest days of the year, with an average of 9h and 6min of daylight.On the first day of the month, sunrise is at 6:56 am and sunset at 4:13 pm. On the last day of December, sunrise is at 7:15 am and sunset at 4:22 pm EST.
Sunshine
In Chelmsford, the average sunshine in December is 4.9h.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 minimal health hazard from exposure to the Sun's UV rays for ordinary individuals.Note: During December, 2 as the daily maximum UV index converts into the following advice:
Protection from prolonged sun exposure is necessary for babies, children, and individuals with sensitive skin. Considering the strength of solar radiation at midday, one should avoid direct Sun exposure. On days when the sun blazes, arm yourself with sunglasses that block UVA and UVB radiation. Take precaution! The reflection from snow can almost double the UV radiation of the Sun.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
How cold is it in December?
What is the average humidity in December?
What is the wettest month?
How many days does it rain in December?
How many days does it snow in December?
What is the month with the shortest days?
How many hours of daylight does Chelmsford have in December?
When are sunrise and sunset in December in Chelmsford?
How long on average sun shines in December?
When is the lowest UV index?
What is the UV index reading in December?
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).
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).
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).
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%).
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").
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).
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").
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).
Average daylight in December /
Average sunshine in December
Chelmsford, MA
- Average daylight in December: 9h and 1min
The month with the longest days is June (Average daylight: 15h and 18min).
The month with the shortest days is December (Average daylight: 9h and 6min).
- Average sunshine in December: 4h and 5min
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).
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).
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).
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).
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).
Chelmsford, Massachusetts, USA
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