The highest day temperature in September 2025 was 94°F. The lowest night temperature was 74°F. The average values for day and night temperatures during September were 89.7°F и 84.2°F respectivly.

The average sea surface temperature in September 2025 for Galveston Island was 89.5°F. The maximum and minimum values were 87.4°F and 91.6°F respectively.

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

Precipitation total in September for Galveston Island is 1.4 in. It makes september one of the most rainy months of the year.

The average wind speed in September is 8.6 mph. It makes September one of the most windless months of the year for Galveston 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 Galveston Island in September is 8.0 hours.