The highest day temperature in September 2025 was 79°F. The lowest night temperature was 55°F. The average values for day and night temperatures during September were 70.3°F и 66.0°F respectivly.

The average sea surface temperature in September 2025 for Siasconset was 68.0°F. The maximum and minimum values were 66.2°F and 70.6°F respectively.

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

Precipitation total in September for Siasconset is 0.8 in. It makes september one of the least rainy months of the year.

The average wind speed in September is 14.6 mph. It makes September one of the most windless 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 September is 7.2 hours.