September weather forecast and climate
Longboat Key, FL

The first month of the autumn, September, is still a hot month in Longboat Key, Florida, with average temperature varying between 77.4°F (25.2°C) and 86.9°F (30.5°C).

Temperature

In September, the average high-temperature is almost the same as in August - a still hot 86.9°F (30.5°C). The average low-temperature, in Longboat Key, is 77.4°F (25.2°C).

Heat index

The average heat index in September is calculated to a torrid 99.9°F (37.7°C). Take special precautions - heat exhaustion and heat cramps are expected. Heatstroke may occur with lengthy activity.
Take into consideration that the heat index values are calculated for shade and light wind conditions. With the 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 'real feel', 'felt air temperature', 'apparent temperature', or 'feels like', is a measure of how hot it feels when the actual air humidity is factored in. Additional factors like wind, differences in body mass, height, and shape, pregnancy, and activity influence one's weather impression. Be aware that direct exposure to sunlight increases heat impact, and may raise the heat index additionally, by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly important for children. Young children are generally more endangered than adults, as they usually less sweat. And also, due to larger skin surface relative to their small bodies and higher heat production as a result of their activity.
The human body cools itself through perspiration, as excessive warmth is removed from the body through sweat evaporation. When the relative humidity is high, the evaporation rate is reduced. The warmth is removed from the body at a lower rate, causing the body to retain more heat than it would in dry air. When heat gain exceeds the level the body can remove, body temperature begins to rise, and heat-related illnesses and disorders may develop.

Humidity

The average relative humidity in Longboat Key, Florida, is 75%.

Rainfall

In Longboat Key, Florida, in September, it is raining for 23.5 days, with typically 4.61" (117mm) of accumulated precipitation. Throughout the year, there are 183.1 rainfall days, and 34.92" (887mm) of precipitation is accumulated.

Ocean temperature

In September, the average ocean temperature in Longboat Key is 84.7°F (29.3°C).
Note: 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.

Daylight

The average length of the day in Longboat Key is 12.3h.

Sunshine

The average sunshine in Longboat Key is 9h.

UV index

Months with the highest UV index in Longboat Key, Florida, are May through September, with an average maximum UV index of 7. A UV Index of 6 to 7 symbolizes a high threat to health from the exposure to the Sun's UV radiation for the average person.
Note: In September, the average maximum UV index of 7 translate into the following recommendations:
Take precautions against overexposure. Protection against sun damage is needed. The Sun's UV radiation is most powerful between 10 a.m. and 4 p.m. To the extent possible, limit exposure to the direct sun during these hours. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes. Caution! The reflection of sand and water significantly increases the intensity of the Sun's UV radiation.

What is the temperature in September in Longboat Key?

In Longboat Key, in September, the average high-temperature is 86.9°F (30.5°C), and the average low-temperature is 77.4°F (25.2°C). In September, the average heat index (a.k.a. 'felt air temperature', 'feels like'), that factores the actual air temperature with the relative humidity, is appraised at 99.9°F (37.7°C).

What is the average humidity in September in Longboat Key?

In Longboat Key, Florida, the average relative humidity in September is 75%.

How many days does it rain in September in Longboat Key?

In September, the rain falls for 23.5 days. Throughout September, 4.61" (117mm) of precipitation is accumulated.

What is the ocean temperature in September in Longboat Key?

In Longboat Key, Florida, in September, the average water temperature is 84.7°F (29.3°C). 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.

How many hours of daylight does Longboat Key have in September?

In Longboat Key, Florida, the average length of the day in September is 12.3h.

How many hours of sunshine does Longboat Key have in September?

In September, the average sunshine in Longboat Key is 9h.

What are the months with the highest UV index in Longboat Key?

Months with the highest UV index in Longboat Key, Florida, are May through September, with an average maximum UV index of 7.

What is the UV index reading in September in Longboat Key?

In Longboat Key, the average daily maximum UV index in September is 7. A UV Index reading of 6 to 7 represents a high hazard to health from the exposure to the Sun's UV radiation.
Average temperature in September - Longboat Key, FL
  • Average high temperature in September: 86.9°F

The warmest month (with the highest average high temperature) is August (88.5°F).
The month with the lowest average high temperature is January (68.5°F).

  • Average low temperature in September: 77.4°F

The month with the highest average low temperature is August (79.7°F).
The coldest month (with the lowest average low temperature) is January (56.1°F).

Average pressure in September - Longboat Key, FL
  • Average pressure in September: 29.95"

The month with the highest atmospheric pressure is January (30.13").
The month with the lowest atmospheric pressure is September (29.95").

Average wind speed in September - Longboat Key, FL
  • Average wind speed in September: 7.2mph

The windiest month (with the highest average wind speed) is January (9.3mph).
The calmest month (with the lowest average wind speed) is July (6.4mph).

Average humidity in September - Longboat Key, FL
  • Average humidity in September: 75%

The month with the highest relative humidity is December (76%).
Months with the lowest relative humidity are March, April and May (72%).

Average rainfall in September - Longboat Key, FL
  • Average rainfall in September: 4.61"

The wettest month (with the highest rainfall) is August (6.42").
The driest months (with the least rainfall) are February and November (1.06").

Average rainfall days in September - Longboat Key, FL
  • Average rainfall days in September: 23.5 days

The month with the highest number of rainy days is August (26.8 days).
Months with the least rainy days are January, February and November (8.3 days).

Average sea temperature in September - Longboat Key, FL
  • Average sea temperature in September: 84.8°F

The best month for swimming (with the highest average sea temperature) is August (86.7°F).
The coldest month (with the lowest average sea temperature) is January (64.1°F).

Average daylight in September / Average sunshine in September - Longboat Key, FL
  • Average daylight in September: 12.3h

The month with the longest days is June (Average daylight: 13.9h).
The month with the shortest days is December (Average daylight: 10.4h).

  • Average sunshine in September: 9h

The month with the most sunshine is May (Average sunshine: 11.1h).
The month with the least sunshine is December (Average sunshine: 6.5h).

Average sunshine days in September - Longboat Key, FL
  • Average sunshine days in September: 4.5 days

The month with the most sunshine days is January (21.1 days).
The month with the least sunshine days is August (2.5 days).

Average UV index in September - Longboat Key, FL
  • Average UV index in September: 7

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

Average cloud cover in September - Longboat Key, FL
  • Average cloud cover in September: 28

Months with the most cloud cover are January and December (Cloud cover 30).
The month with the least cloud cover is May (Cloud cover 22).

Average visibility in September - Longboat Key, FL
  • Average visibility in September: 6mi

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