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December Weather in Portsmouth, United States

Last updated: June 24, 2025

In December, the average temperature in Portsmouth, United States hovers around 4°C (39°F), with a minimum dip to -13°C (9°F) and a maximum rise to 16°C (61°F). Expect about 147 mm (5.8 in) of precipitation spread across 11 days, accompanied by an average humidity of 80%. Stay prepared for a chilly and wet experience!

December Temperature in Portsmouth

In December in Portsmouth, the average temperature is 4°C (39°F), with maxima reaching up to 16°C (61°F) and minima dropping as low as -13°C (9°F). It’s essential to pack warm clothing to stay comfortable during your travels.

December Weather in Portsmouth: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in Portsmouth, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Portsmouth, December typically has an average temperature of 4°C (39°F), with highs reaching up to 16°C (61°F) and lows dropping to around -13°C (9°F).
JanFebMarAprMayJunJulAugSepOctNovDec353638465464727267594839
Data source: Temperature data for Portsmouth generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

December Precipitation in Portsmouth

In Portsmouth in December, the total precipitation amount is 147 mm (5.8 in), occurring over the course of 11 days.

December Precipitation Trends in Portsmouth

The chart displays monthly precipitation patterns in Portsmouth, with values for each month alongside December’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how December’s conditions compare to those of other months. In Portsmouth, December typically receives around 147 mm (5.8 inches) of precipitation spread over approximately 11 days.
JanFebMarAprMayJunJulAugSepOctNovDec9612111914713310410489110169117147
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Portsmouth

In Portsmouth in December, humidity is 80%. With an average temperature of 4°C (39°F), this humidity feels like a damp chill that seeps into your bones, making travel uncomfortable and requiring extra layers to stay warm while navigating through the misty streets.

December Average Humidity in Portsmouth

This chart illustrates the average monthly humidity levels in Portsmouth, with December’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In December, average humidity in Portsmouth is approximately 80%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%84%82%79%75%78%76%76%76%75%80%80%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Portsmouth

In Portsmouth in December, the maximum UV index is 2, which corresponds to a low exposure category. With this level of UV radiation, the time to burn is approximately 45 minutes. To learn more about the hourly UV index in Portsmouth, you can visit Hourly UV Index in Portsmouth.

Maximum UV Index Levels in Portsmouth for December

The chart shows the monthly maximum UV Index (UVI) for Portsmouth in December, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In December, the maximum UV index in Portsmouth typically reaches 2, which falls under the low exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3568910998642
Data source: Portsmouth December UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How December Weather in Portsmouth Compares to Other Months

Weather in Portsmouth varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Portsmouth, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Portsmouth, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather1°C (35°F)95 mm (3.8 inches)84%moderate
February Weather2°C (36°F)121 mm (4.8 inches)84%moderate
March Weather3°C (39°F)119 mm (4.7 inches)82%high
April Weather8°C (46°F)147 mm (5.8 inches)79%very high
May Weather12°C (55°F)132 mm (5.2 inches)75%very high
June Weather18°C (64°F)104 mm (4.1 inches)78%very high
July Weather22°C (72°F)104 mm (4.1 inches)76%very high
August Weather22°C (73°F)89 mm (3.5 inches)76%very high
September Weather20°C (67°F)110 mm (4.3 inches)75%very high
October Weather15°C (60°F)169 mm (6.7 inches)75%high
November Weather9°C (48°F)117 mm (4.6 inches)80%moderate
December Weather4°C (39°F)147 mm (5.8 inches)80%low

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