Weather in Grand Isle: September
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Average day temperature: | 82.4°F |
| Average night temperature: | 80.0°F | |
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Sea water temperature: | 84.7°F |
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Number of sunny days: | 15 days |
| Day length: | 11.9 - 12.7 hours | |
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Number of rainy days: | 4 days |
| Precipitation totals: | 2.2 in. | |
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forecast
| Grand Isle |
temperature
| Grand Isle |
Air temperature in September, °F
The highest day temperature during September of 2025 was 85°F. At the same time the lowest night temperature was 79°F. Daily and nightly averages during September were 83.2°F and 81.0°F.
Sea water temperature in Grand Isle in September, °F
The average sea water temperature in September of 2025 was 85.2°F. The highest and lowest sea temperatures during the month were 88.2°F and 83.8°F.
Mostly all days in September are sunny but cloudy days are also possible.
Precipitation total in September, in.
Precipitation total value in Grand Isle in September is 2.2 in. Other months of the year show relatively similar values.
The average wind speed value in September is 10.2 mph It makes September one of the least windy months of the year.
This chart shows average number of hours during the day when sunlight can reach the ground. It depends on day length and cloudiness during the day. The average number of sunny hours in September is: 8.1.
Best time for vacation in Grand Isle
Grand Isle on a weather map
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