January Weather in Portsmouth, United States

Last updated: June 24, 2025

In January, the average temperature in Portsmouth, United States hovers around 2°C (35°F). Be prepared for a chilly range, where temperatures can dip as low as -19°C (-2°F) and occasionally rise to a warm 22°C (71°F). During this month, you can expect 85 mm (3.3 in) of precipitation over approximately 9 days, contributing to a high average humidity of 88%.

January Temperature in Portsmouth

In January in Portsmouth, the average temperature is 2°C (35°F), with maximums reaching 22°C (71°F) and minimums dropping as low as -19°C (-2°F). Be prepared for a wide range of temperatures when traveling to Portsmouth during this month.

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

The chart illustrates January 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, January typically has an average temperature of 2°C (35°F), with highs reaching up to 22°C (71°F) and lows dropping to around -19°C (-2°F).

Data source: Temperature data for Portsmouth generated using information from the Copernicus Climate Change Service.

January Precipitation in Portsmouth

In Portsmouth in January, the precipitation amount is 85 mm (3.3 in) over the course of 9 days.

January Precipitation Trends in Portsmouth

The chart displays monthly precipitation patterns in Portsmouth, with values for each month alongside January’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how January’s conditions compare to those of other months. In Portsmouth, January typically receives around 85 mm (3.3 inches) of precipitation spread over approximately 9 days.

Data source: Precipitation data for January generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

January Humidity in Portsmouth

In Portsmouth in January, humidity is 88%. With an average temperature of 2°C (35°F), this humidity feels like you're wrapped in a cold, damp blanket, making outdoor activities uncomfortable and travel challenging due to the chill seeping into your bones.

January Average Humidity in Portsmouth

This chart illustrates the average monthly humidity levels in Portsmouth, with January’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In January, average humidity in Portsmouth is approximately 88%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for January generated using information from the Copernicus Climate Change Service.

January UV Index in Portsmouth

In Portsmouth in January, the maximum UV index is 3, which corresponds to a moderate Exposure Category. The time to burn is approximately 30 minutes. For more details on the hourly UV index in Portsmouth, you can check the information here.

Maximum UV Index Levels in Portsmouth for January

The chart shows the monthly maximum UV Index (UVI) for Portsmouth in January, 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 January, the maximum UV index in Portsmouth typically reaches 3, which falls under the moderate exposure category.

Data source: Portsmouth January 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 January 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 January’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 January’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	2°C (35°F)	85 mm (3.3 inches)	88%	moderate
February Weather	4°C (39°F)	124 mm (4.9 inches)	88%	moderate
March Weather	8°C (47°F)	106 mm (4.2 inches)	87%	high
April Weather	13°C (55°F)	128 mm (5.0 inches)	85%	very high
May Weather	19°C (66°F)	128 mm (5.0 inches)	81%	very high
June Weather	23°C (73°F)	157 mm (6.2 inches)	82%	very high
July Weather	25°C (78°F)	107 mm (4.2 inches)	81%	very high
August Weather	24°C (75°F)	120 mm (4.7 inches)	73%	very high
September Weather	21°C (71°F)	109 mm (4.3 inches)	73%	very high
October Weather	15°C (60°F)	116 mm (4.5 inches)	78%	high
November Weather	7°C (45°F)	77 mm (3.0 inches)	89%	moderate
December Weather	4°C (40°F)	112 mm (4.4 inches)	87%	moderate