The highest day temperature in December 2025 was 54°F. The lowest night temperature was 15°F. The average values for day and night temperatures during December were 36.9°F и 31.5°F respectivly.

The average sea surface temperature in December 2025 for Siasconset was 41.9°F. The maximum and minimum values were 38.4°F and 47.2°F respectively.

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

Precipitation total in December for Siasconset is 1.3 in.

The average wind speed in December is 18.9 mph. It makes December one of the most windy months of the year for Siasconset.

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 Siasconset in December is 4.2 hours.