The highest day temperature in September 2025 was 80°F. The lowest night temperature was 59°F. The average values for day and night temperatures during September were 71.5°F и 66.3°F respectivly.

The average sea surface temperature in September 2025 for Block Island was 70.0°F. The maximum and minimum values were 68.4°F and 71.0°F respectively.

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

Precipitation total in September for Block Island is 1.1 in.

The average wind speed in September is 12.2 mph. It makes September one of the most windless months of the year for Block Island.

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 Block Island in September is 7.7 hours.