The highest day temperature in January 2026 was 57°F. The lowest night temperature was -5°F. The average values for day and night temperatures during January were 28.9°F и 18.7°F respectivly.

The average sea surface temperature in January 2026 for Portsmouth was 40.1°F. The maximum and minimum values were 38.2°F and 41.4°F respectively.

You can expect various weather conditions during January. Be ready for sunny, cloudy or even gloomy days.

Precipitation total in January for Portsmouth is 1.1 in.

The average wind speed in January is 9.7 mph. It makes January the most windy month of the year for Portsmouth.

We are using day length and cloud cover information for each day of the month to calculate averages for this chart. Average sunny hours for Portsmouth in January is 4.9 hours.