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
With December's onset, the weather shows a temperature decrease, transitioning from a frosty 47.1°F (8.4°C) in November to a cold 37.6°F (3.1°C). Throughout December, the temperature in Portsmouth tends to fall to a consistent average low of 28°F (-2.2°C).Humidity
In December, the average relative humidity is 78%.Rainfall
In Portsmouth, in December, during 11.5 rainfall days, 2.8" (71mm) of precipitation is typically accumulated. Throughout the year, there are 144.2 rainfall days, and 27.48" (698mm) of precipitation is accumulated.Snowfall
January through April, October through December are months with snowfall. In Portsmouth, in December, snow falls for 7.5 days, with typically accumulated 3.9" (99mm) of snow. In Portsmouth, during the entire year, snow falls for 35.2 days and aggregates up to 16.97" (431mm) of snow.Ocean temperature
In Portsmouth, the average seawater temperature in December is 45.9°F (7.7°C).Note: It is advised against swimming in 45.9°F (7.7°C) when it drops below 50°F (10°C). Such temperatures can cause extreme cold shock, leading to hyperventilation.
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 6:55 am and sunset at 4:09 pm. On the last day of December, sunrise is at 7:14 am and sunset at 4:18 pm EST.
Sunshine
February and December, with an average of 4.8h of sunshine, are months with the least 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 exposure to the Sun's UV radiation for average individuals.Note: A daily maximum UV index of 2 in December translates into the following instructions:
The majority are not significantly affected by prolonged sun exposure. Infants, children, and those with fair skin must always have protection. The Sun's UV radiation is especially harmful around midday, so reduce exposure and stay safe. It's wise to wear UVA and UVB-blocking sunglasses when the sun shines brightly. On your guard! Snow's reflection can almost double the intensity of the Sun's UV radiation.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
How cold does it get in December?
What is the average humidity in December?
How many days does it rain in December?
How many days does it snow in December?
How cold is the water in December?
What is the month with the shortest days?
How many hours of daylight does Portsmouth have in December?
When are sunrise and sunset in December?
What are the months with the least sunshine?
How many hours of sunshine does Portsmouth have in December?
When is the lowest UV index?
What is the UV index reading in December?
Average temperature in December
Portsmouth, NH
- Average high temperature in December: 37.6°F
The warmest month (with the highest average high temperature) is July (76.3°F).
The month with the lowest average high temperature is January (31.8°F).
- Average low temperature in December: 28°F
The month with the highest average low temperature is July (62.6°F).
The coldest month (with the lowest average low temperature) is January (21.2°F).
Average pressure in December
Portsmouth, NH
- 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 (29.92"Hg).
Average wind speed in December
Portsmouth, NH
- Average wind speed in December: 10.8mph
The windiest month (with the highest average wind speed) is January (11.7mph).
The calmest month (with the lowest average wind speed) is July (6.6mph).
Average humidity in December
Portsmouth, NH
- Average humidity in December: 78%
The month with the highest relative humidity is June (80%).
The months with the lowest relative humidity are April and November (75%).
Average rainfall in December
Portsmouth, NH
- Average rainfall in December: 2.8"
The wettest month (with the highest rainfall) is October (2.83").
The driest month (with the least rainfall) is September (1.54").
Average rainfall days in December
Portsmouth, NH
- Average rainfall days in December: 11.5 days
The month with the highest number of rainy days is June (15 days).
The month with the least rainy days is January (7.5 days).
Average snowfall in December
Portsmouth, NH
- Average snowfall in December: 3.9"
The month with the highest snowfall is January (4.02").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in December
Portsmouth, NH
- Average snowfall days in December: 7.5 days
The month with the highest number of snowfall days is January (8.8 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average sea temperature in December
Portsmouth, NH
- Average sea temperature in December: 45.8°F
The best month for swimming (with the highest average sea temperature) is August (65.6°F).
The coldest month (with the lowest average sea temperature) is March (38.5°F).
Average daylight in December /
Average sunshine in December
Portsmouth, NH
- 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 months with the least sunshine are February and December (Average sunshine: 4h and 48min).
Average sunshine days in December
Portsmouth, NH
- Average sunshine days in December: 14.5 days
The month with the most sunshine days is September (16.8 days).
The month with the least sunshine days is April (13.2 days).
Average UV index in December
Portsmouth, NH
- 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
Portsmouth, NH
- Average cloud cover in December: 47
The month with the most cloud cover is March (Cloud cover 50).
The month with the least cloud cover is August (Cloud cover 29).
Average visibility in December
Portsmouth, NH
- 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).
Portsmouth, New Hampshire, USA
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