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 sea temperature 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
The shift from November to December includes a minor decrease in the average high-temperature, lightly dropping from a cool 51.3°F (10.7°C) to a frosty 43.7°F (6.5°C). Hyannis experiences a subtle drop in temperature during the December nights, recording an average of 36.5°F (2.5°C).Humidity
In Hyannis, the average relative humidity in December is 75%.Rainfall
In Hyannis, during December, the rain falls for 14.2 days and regularly aggregates up to 3.62" (92mm) of precipitation. Throughout the year, there are 157.2 rainfall days, and 31.77" (807mm) of precipitation is accumulated.Snowfall
Months with snowfall are January through April and December. December is the first month it typically snows. Throughout December, in the average 4.4 snowfall days, it receives 0.87" (22mm) of snow. In Hyannis, during the entire year, snow falls for 24.1 days and aggregates up to 6.1" (155mm) of snow.Ocean temperature
In Hyannis, the average seawater temperature in December is 46°F (7.8°C).Note: Dipping into 46°F (7.8°C) below 50°F (10°C) needs protective wear, or you'd face cold shock and breathing issues swiftly. Meanwhile, a slight swim around 55.4°F (13°C) feels cold to the bone.
Daylight
The month with the shortest days is December, with an average of 9h and 12min of daylight.On the first day of the month, sunrise is at 6:49 am and sunset at 4:11 pm. On the last day of December, sunrise is at 7:07 am and sunset at 4:20 pm EST.
Sunshine
The month with the least sunshine is December, with an average of 4.6h of sunshine.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 estimate of 2, and below, represents a low threat to health from unprotected exposure to Sun's UV rays for the ordinary person.Note: A daily high UV index of 2 in December leads to these guidelines:
Long-term sun exposure is typically not a concern for most. However, those with sensitive skin, infants, and children must always have protection. Midday is when the Sun's radiation is strongest; avoid prolonged exposure during this time. For holistic sun protection encompassing the eyes, ears, face, and neck, a wide-brim hat is key. Beware! Reflection from snow can magnify the Sun's UV radiation nearly twofold.
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Data Sources | Weather Forecasting & Climate
Frequently asked questions
Is it cold during December?
What is the average humidity in December?
How many days does it rain in December?
When does it start to snow?
What is the water temperature in December?
What is the month with the shortest days?
How many hours of daylight does Hyannis have in December?
When is the sunrise / sunset in December?
What is the month with the least sunshine?
How long on average sun shines in December?
What is the month with the lowest UV index?
How high is the UV index in December in Hyannis?
Average temperature in December
Hyannis, MA
- Average high temperature in December: 43.7°F
The warmest month (with the highest average high temperature) is August (72.5°F).
The month with the lowest average high temperature is January (38.3°F).
- Average low temperature in December: 36.5°F
The month with the highest average low temperature is August (68.2°F).
The coldest month (with the lowest average low temperature) is January (30.4°F).
Average pressure in December
Hyannis, MA
- Average pressure in December: 30.03"Hg
The month with the highest atmospheric pressure is November (30.06"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).
Average wind speed in December
Hyannis, MA
- Average wind speed in December: 16.1mph
The windiest month (with the highest average wind speed) is January (16.5mph).
The calmest month (with the lowest average wind speed) is August (10.6mph).
Average humidity in December
Hyannis, MA
- Average humidity in December: 75%
The month with the highest relative humidity is July (84%).
The month with the lowest relative humidity is November (74%).
Average rainfall in December
Hyannis, MA
- Average rainfall in December: 3.62"
The wettest month (with the highest rainfall) is October (3.7").
The driest month (with the least rainfall) is August (1.73").
Average rainfall days in December
Hyannis, MA
- Average rainfall days in December: 14.2 days
The month with the highest number of rainy days is April (15.8 days).
The month with the least rainy days is February (10.3 days).
Average snowfall in December
Hyannis, MA
- Average snowfall in December: 0.87"
The month with the highest snowfall is March (1.93").
The months with the least snowfall are May, June, July, August, September, October and November (0").
Average snowfall days in December
Hyannis, MA
- Average snowfall days in December: 4.4 days
The month with the highest number of snowfall days is February (7.1 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average sea temperature in December
Hyannis, MA
- Average sea temperature in December: 46.1°F
The best month for swimming (with the highest average sea temperature) is August (67.5°F).
The coldest month (with the lowest average sea temperature) is March (39°F).
Average daylight in December /
Average sunshine in December
Hyannis, MA
- Average daylight in December: 9h and 1min
The month with the longest days is June (Average daylight: 15h and 6min).
The month with the shortest days is December (Average daylight: 9h and 12min).
- Average sunshine in December: 4h and 4min
The month with the most sunshine is August (Average sunshine: 10h and 48min).
The month with the least sunshine is December (Average sunshine: 4h and 36min).
Average sunshine days in December
Hyannis, MA
- Average sunshine days in December: 12.6 days
The month with the most sunshine days is August (17.7 days).
The month with the least sunshine days is February (11.4 days).
Average UV index in December
Hyannis, MA
- Average UV index in December: 2
The months with the highest UV index are 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
Hyannis, MA
- Average cloud cover in December: 50
The months with the most cloud cover are February and December (Cloud cover 50).
The month with the least cloud cover is August (Cloud cover 27).
Average visibility in December
Hyannis, 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).
Hyannis, Massachusetts, USA
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