September weather forecast
Grand Isle, LA

The scenic Grand Isle, Louisiana, with a view of the numerous houses and the extended piers onto the calm seawater
The scenic Grand Isle, Louisiana, with a view of the numerous houses and the extended piers onto the calm seawater

Weather in September

The first month of the autumn, September, is also a moderately hot month in Grand Isle, Louisiana, with an average temperature fluctuating between 84.6°F (29.2°C) and 78.8°F (26°C).

Temperature

In Grand Isle, the average high-temperature in September is relatively the same as in August - a moderately hot 84.6°F (29.2°C). The average low-temperature, in September, is 78.8°F (26°C).

Heat index

In September, the average heat index is calculated to be a tropical 93.2°F (34°C). Take extra precautions, as heat cramps and heat exhaustion are possible. Sustained activity may result in heatstroke.
Take into consideration that the heat index values are calculated for shade and light wind conditions. With exposure to direct sunlight, the heat index may be increased by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature', 'feels like', 'real feel', or 'felt air temperature', is a measure that combines air temperature and relative humidity into a single value that indicates how hot the weather feels. This effect is individual, with diverse people perceiving weather differently for numerous reasons (differences in body mass, height, and shape, metabolic differences, wind), and activity. Be aware that direct exposure to sunlight increases heat impact and may raise the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are especially crucial for babies and toddlers. Children are often less aware of the need to rest and re-hydrate. Thirst is a late sign of dehydration - it is vital to remain hydrated, particularly during prolonged physical activities.

Humidity

The average relative humidity in September in Grand Isle is 73%.

Rainfall

In Grand Isle, it is raining for 17.3 days, with typically 2.17" (55mm) of accumulated precipitation. Throughout the year, there are 151.9 rainfall days, and 22.01" (559mm) of precipitation is accumulated.

Snowfall

In Grand Isle, snow does not fall in February through December.

Ocean temperature

In Grand Isle, Louisiana, the average seawater temperature in September is 83.8°F (28.8°C).
Note: For swimming, diving, and other water activities, temperatures between 77°F (25°C) and 84.2°F (29°C) are perceived as very enjoyable and pleasurable for prolonged periods without feeling uncomfortable.

Daylight

In September, the average length of the day is 12h and 20min.
On the first day of September in Grand Isle, Louisiana, sunrise is at 6:37 am and sunset at 7:22 pm. On the last day of the month, sunrise is at 6:52 am and sunset at 6:47 pm CDT.

Sunshine

In Grand Isle, the average sunshine in September is 10.2h.

UV index

May through September, with an average maximum UV index of 7, are months with the highest UV index. A UV Index of 6 to 7 symbolizes a high health vulnerability from unsafe exposure to UV radiation for ordinary individuals.
Note: In September, the average maximum UV index of 7 translate into the following recommendations:
Take precautions and utilize sun safety practices. Protection against skin and eye damage is required. Seek shade and minimize exposure to direct Sun in a period between 10 a.m. and 4 p.m. when UV radiation is most intense; keep in mind that shade structures like parasols or canopies do not provide perfect sun protection. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects. Beware! The strength of the UV rays is significantly increased by the reflection of the water and sand.
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FAQ

What is the temperature in September in Grand Isle?

The average high-temperature, in September, in Grand Isle, is 84.6°F (29.2°C), while the average low-temperature is 78.8°F (26°C). in September, the average heat index (a.k.a. 'felt air temperature', 'apparent temperature'), which factors the actual air temperature with the relative humidity, is calculated to be 93.2°F (34°C).

What is the average humidity in September in Grand Isle?

In September, the average relative humidity is 73%.

How much does it rain in Grand Isle in September?

In Grand Isle, during September, the rain falls for 17.3 days and regularly aggregates up to 2.17" (55mm) of precipitation.

When it does not snow in Grand Isle?

In Grand Isle, snow does not fall in February through December.

What is the ocean temperature in September in Grand Isle?

In Grand Isle, in September, the average water temperature is 83.8°F (28.8°C). For any water activity, surface water temperatures between 77°F (25°C) and 84.2°F (29°C) are considered as excellent and extremely pleasant for lengthened periods.

How many hours of daylight does Grand Isle have in September?

In September, the average day length in Grand Isle, Louisiana, is 12h and 20min.

When is the sunrise / sunset in September in Grand Isle?

On the first day of September in Grand Isle, sunrise is at 6:37 am and sunset at 7:22 pm. On the last day of the month, sunrise is at 6:52 am and sunset at 6:47 pm CDT.

How many hours of sunshine does Grand Isle have in September?

In Grand Isle, the average sunshine duration in September is 10.2h.

What is the month with the highest UV index in Grand Isle?

The months with the highest UV index are May through September, with an average maximum UV index of 7.

How high is the UV index in September in Grand Isle?

The average daily maximum UV index in September in Grand Isle, Louisiana, is 7. A UV Index estimate of 6 to 7 represents a high health vulnerability from exposure to the Sun's UV radiation.
Average humidity
Average rainfall days
Average snowfall days
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Grand Isle, LA

Average temperature in September - Grand Isle, LA
  • Average high temperature in September: 84.6°F

The warmest months (with the highest average high temperature) are July and August (86.9°F).
The month with the lowest average high temperature is January (61.7°F).

  • Average low temperature in September: 78.8°F

The month with the highest average low temperature is August (81.3°F).
The coldest month (with the lowest average low temperature) is January (53.1°F).

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Average pressure in September
Grand Isle, LA

Average pressure in September - Grand Isle, LA
  • Average pressure in September: 29.96"Hg

The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is September (29.96"Hg).

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Average wind speed in September
Grand Isle, LA

Average wind speed in September - Grand Isle, LA
  • Average wind speed in September: 8.8mph

The windiest month (with the highest average wind speed) is January (12.4mph).
The calmest month (with the lowest average wind speed) is July (8mph).

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Average humidity in September
Grand Isle, LA

Average humidity in September - Grand Isle, LA
  • Average humidity in September: 73%

The months with the highest relative humidity are February and December (78%).
The month with the lowest relative humidity is October (71%).

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Average rainfall in September
Grand Isle, LA

Average rainfall in September - Grand Isle, LA
  • Average rainfall in September: 2.17"

The wettest month (with the highest rainfall) is August (4.72").
The driest months (with the least rainfall) are February and April (0.87").

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Average rainfall days in September
Grand Isle, LA

Average rainfall days in September - Grand Isle, LA
  • Average rainfall days in September: 17.3 days

The month with the highest number of rainy days is August (20.7 days).
The month with the least rainy days is November (7.5 days).

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Average snowfall days in September
Grand Isle, LA

Average snowfall days in September - Grand Isle, LA
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (0.1 days).
The months with the least snowfall days are February, March, April, May, June, July, August, September, October, November and December (0 days).

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Average sea temperature in September
Grand Isle, LA

Average sea temperature in September - Grand Isle, LA
  • Average sea temperature in September: 83.8°F

The best month for swimming (with the highest average sea temperature) is August (87.5°F).
The coldest month (with the lowest average sea temperature) is January (61.4°F).

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Average daylight in September /
Average sunshine in September
Grand Isle, LA

Average daylight in September / Average sunshine in September - Grand Isle, LA
  • Average daylight in September: 12h and 20min

The month with the longest days is June (Average daylight: 13h and 59min).
The month with the shortest days is December (Average daylight: 10h and 19min).

  • Average sunshine in September: 10h and 12min

The month with the most sunshine is June (Average sunshine: 11h and 0min).
The month with the least sunshine is December (Average sunshine: 5h and 24min).

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Average sunshine days in September
Grand Isle, LA

Average sunshine days in September - Grand Isle, LA
  • Average sunshine days in September: 8.6 days

The month with the most sunshine days is November (19.5 days).
The month with the least sunshine days is August (6.5 days).

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Average UV index in September
Grand Isle, LA

Average UV index in September - Grand Isle, LA
  • Average UV index in September: 7

The months with the highest UV index are May, June, July, August and September (UV index 7).
The months with the lowest UV index are January and December (UV index 4).

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Average cloud cover in September
Grand Isle, LA

Average cloud cover in September - Grand Isle, LA
  • Average cloud cover in September: 25

The month with the most cloud cover is December (Cloud cover 42).
The month with the least cloud cover is May (Cloud cover 23).

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Average visibility in September
Grand Isle, LA

Average visibility in September - Grand Isle, LA
  • Average visibility in September: 6mi

The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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