Portsmouth
New Hampshire, USA
Long-term weather forecast
Long-term weather forecast

December weather forecast and climate
Portsmouth, NH

Bright neon lights and buildings next to the very calm waters of the iconic Piscataqua River in Portsmouth, New Hampshire, the clear dusk sky in close up view
Bright neon lights and buildings next to the very calm waters of the iconic Piscataqua River in Portsmouth, New Hampshire, the clear dusk sky in close up view
The first month of the winter, December, is still a cold month in Portsmouth, New Hampshire, with average temperature ranging between max 34°F (1.1°C) and min 21°F (-6.1°C).

Temperature

In December, the average high-temperature decreases, from a frosty 48°F (8.9°C) in November, to a cold 34°F (1.1°C). The average low-temperature, in Portsmouth, is 21°F (-6.1°C).

Rainfall

In Portsmouth, in December, it is raining for 12 days, with typically 4.2" (107mm) of accumulated precipitation. In Portsmouth, New Hampshire, during the entire year, the rain falls for 125 days and collects up to 42.4" (1078mm) of precipitation.

Ocean temperature

In December, the average ocean temperature is 45.9°F (7.7°C). Swimming in 45.9°F (7.7°C) is considered dangerous. Unprotected immersion in temperatures below 50°F (10°C) causes quickly maximum intensity cold shock with hyperventilation.

Daylight

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

Sunshine

Months with the least sunshine are January, November and December, with an average of 5h of sunshine.

UV index

Months with the lowest UV index are January and December, with an average maximum UV index of 1. A UV Index estimate of 2, and below, represents a minimal health vulnerability from the exposure to the Sun's UV rays for average individuals.
The daily maximum UV index of 1 in December interpret into the following advice:
Most people can stay in the Sun for up to 1 hour without burning, apart from children that always must be protected from 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.

What is the temperature in December in Portsmouth?

The average high-temperature, in December, is 34°F (1.1°C), while the average low-temperature is 21°F (-6.1°C).

How many days does it rain in December in Portsmouth?

In Portsmouth, in December, it is raining for 12 days, with typically 4.2" (107mm) of accumulated precipitation.

What is the ocean temperature in December in Portsmouth?

In Portsmouth, in December, the average water temperature is 45.9°F (7.7°C). Swimming in 45.9°F (7.7°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.

What is the month with the shortest days in Portsmouth?

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

How many hours of daylight does Portsmouth have in December?

In December, the average length of the day in Portsmouth, New Hampshire, is 9.1h.

What is the month with the least sunshine in Portsmouth?

January, November and December, with an average of 5h of sunshine, are months with the least sunshine in Portsmouth, New Hampshire.

How many hours of sunshine does Portsmouth have in December?

In Portsmouth, the average sunshine in December is 5h.

When is the lowest UV index in Portsmouth?

Months with the lowest UV index in Portsmouth, New Hampshire, are January and December, with an average maximum UV index of 1.

What is the UV index intensity in December in Portsmouth?

The average daily maximum UV index in December in Portsmouth is 1. A UV Index of 2, and less, symbolizes a low health risk from the exposure to the Sun's UV rays.
Average temperature in December - Portsmouth, NH
  • Average high temperature in December: 34°F

The warmest month (with the highest average high temperature) is July (79°F).
Months with the lowest average high temperature are January and February (32°F).

  • Average low temperature in December: 21°F

The month with the highest average low temperature is July (61°F).
The coldest month (with the lowest average low temperature) is January (16°F).

Average rainfall in December - Portsmouth, NH
  • Average rainfall in December: 4.2"

The wettest month (with the highest rainfall) is November (4.9").
The driest month (with the lowest rainfall) is August (2.8").

Average rainfall days in December - Portsmouth, NH
  • Average rainfall days in December: 12 days

Months with the highest number of rainy days are May and December (12 days).
The month with the lowest number of rainy days is September (8 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: 9.1h

The month with the longest days is June (Average daylight: 15.3h).
The month with shortest days is December (Average daylight: 9.1h).

  • Average sunshine in December: 5h

Months with most sunshine are June, July and August (Average sunshine: 9h).
Months with least sunshine are January, November and December (Average sunshine: 5).

Average UV index in December - Portsmouth, NH
  • Average UV index in December: 1

Months with the highest UV index are June and July (UV index 8).
Months with the lowest UV index are January and December (UV index 1).