The highest day temperature in September 2026 was 91°F. The lowest night temperature was 83°F. The average values for day and night temperatures during September were 88.1°F и 86.4°F respectivly.

The average sea surface temperature in September 2026 for Grand Isle was 90.6°F. The maximum and minimum values were 88.6°F and 92.6°F respectively.

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

Precipitation total in September for Grand Isle is 2.1 in. It makes september one of the most rainy months of the year.

The average wind speed in September is 10.1 mph. It makes September one of the most windless months of the year for Grand Isle.

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 Grand Isle in September is 7.6 hours.