September weather forecastGrand Isle, LA
September
Weather in September
Grand Isle weather in September initiates a shift towards more pleasant conditions, with the highest temperature at 84.6°F (29.2°C) commencing the slow descent into autumn. September begins witnessing shorter days and falling humidity levels, although the sea remains adequately warm for water activities. Rainfall recedes and makes way for drier days, trending towards autumn. With the peak summer gradually fading, the weather changes in September make for an easy transition, without any dramatic shifts, subtly preparing the city for the upcoming fall.Temperature
With the arrival of September, Grand Isle's average high-temperature registers at a moderately hot 84.6°F (29.2°C), indicating a subtle variation from the previous month. Nights during September maintain a steady temperature, averaging at a still warm 78.8°F (26°C).Heat index
The heat index for September is appraised at a tropical 93.2°F (34°C). Undertake additional safety actions, risk of heat cramps and heat exhaustion is significant. Persistent activity may induce heatstroke.Metrics for the heat index primarily focus on shaded spots and light wind conditions. Direct sunlight might cause an increase of up to 15 Fahrenheit (8 Celsius) degrees in the heat index.
Note: The heat index, also known as 'apparent temperature' or 'feels like', is a value derived by merging air temperature with the humidity to convey how the climate feels. One's weather perception can be influenced by a range of factors including metabolic differences, being pregnant, and their level of physical activity. Do note, being directly under sun rays can amplify the heat you feel, potentially raising the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are primarily vital for children. Young ones are generally at greater risk than adults due to their limited sweating ability. In addition, their large skin surface relative to their small bodies and higher heat production from their activities add to their vulnerability.
Humidity
The average relative humidity in September is 73%.Rainfall
In Grand Isle, during September, the rain falls for 17.3 days and regularly aggregates up to 2.17" (55mm) of 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: With water temperature from 77°F (25°C) to 84.2°F (29°C), all water activities are comfortable and delightful, devoid of discomfort even for lengthened periods.
Daylight
In Grand Isle, the average length of the day in September is 12h and 20min.On the first day of September, sunrise is at 6:37 am and sunset at 7:21 pm. On the last day of the month, sunrise is at 6:52 am and sunset at 6:46 pm CDT.
Sunshine
In September, the average sunshine is 10.2h.UV index
May through September, with an average maximum UV index of 7, are months with the highest UV index in Grand Isle. A UV Index reading of 6 to 7 represents a high threat to health from exposure to the Sun's UV rays for the average person.Note: The UV index of 7 during September translates into the following guidance:
Steer clear of overexposure. Fair-skinned individuals can be scorched in less than 20 minutes. The Sun's UV radiation is most potent between the hours of 10 a.m. and 4 p.m. Try to avoid direct sunlight during this time. 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. Take note! Sand and water reflections strengthen the Sun's UV exposure.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
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).
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).
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).
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%).
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").
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).
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).
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).
Average daylight in September /
Average sunshine in September
Grand Isle, LA
- Average daylight in September: 12h and 18min
The month with the longest days is June (Average daylight: 14h and 0min).
The month with the shortest days is December (Average daylight: 10h and 18min).
- 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).
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).
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).
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).
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).
