The highest day temperature in December 2025 was 49°F. The lowest night temperature was 18°F. The average values for day and night temperatures during December were 37.5°F и 33.9°F respectivly.

The average sea surface temperature in December 2025 for Charlestown was 46.1°F. The maximum and minimum values were 41.8°F and 51.2°F respectively.

Most of the days in December are sunny but you can also expect cloudy and gloomy days.

Precipitation total in December for Charlestown is 1.3 in. It makes december one of the most rainy months of the year.

The average wind speed in December is 13.3 mph. It makes December the most windy month of the year for Charlestown.

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 Charlestown in December is 5.2 hours.