September weather forecast
Sanibel, FL

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A large flock of the iconic royal tern birds on the white sandy shores on a typical beach in Sanibel, Florida
A large flock of the iconic royal tern birds on the white sandy shores on a typical beach in Sanibel, Florida

Weather in September

Sanibel's weather shows a subtle shift as September comes around, bringing slightly cooler days and a decrease in rainfall. September signifies the gradual conclusion of the hot season, marking the beginning of the city's transition towards its cooler period. The sea temperature is around 82.3°F (27.9°C) in September, perfect for a refreshing swim or other water activities. With this, September maintains a healthy balance of sunshine hours and daylight, useful for sight-seeing or other leisure pursuits. Despite the climatic changes, Sanibel's September weather sustains the city's appeal with its agreeable temperatures and relatively lower rainfall occurrences.

Temperature

As September takes hold in Sanibel, the average high-temperature is a still tropical 86.5°F (30.3°C), nearly mirroring that of the previous month. Sanibel, in September, registers a nighttime average temperature of 79.2°F (26.2°C).

Heat index

The heat index for September is estimated at a torrid 98.6°F (37°C). Ensure extra safety measures, heat exhaustion and heat cramps are likely. Continuous activity might result in heatstroke.
Research indicates the heat index considers values in shaded locales and with light winds. Under direct sunshine, the heat index values might be elevated by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'felt air temperature' or 'feels like', combines both the air temperature and the humidity level to give a perceived human temperature. The impression of weather on a person can be swayed by additional aspects, including metabolic variations, pregnancy, and activity levels. With the sun shining directly, it's crucial to understand that it can increase the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are highly important 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.
By perspiring, the human body can shed its excessive warmth since evaporated sweat cools it off. Under high air temperature coupled with high humidity (high heat index), the body's perspiration is reduced, intensifying the sensation of heat. Heat-related disorders may develop if heat gain in the body overshadows its cooling capacity, leading to elevated temperatures.

Humidity

In Sanibel, the average relative humidity in September is 75%.

Rainfall

In Sanibel, Florida, during September, the rain falls for 25.3 days and regularly aggregates up to 6.18" (157mm) of precipitation. In Sanibel, during the entire year, the rain falls for 190.9 days and collects up to 41.73" (1060mm) of precipitation.

Ocean temperature

In Sanibel, Florida, in September, the average water temperature is 85.3°F (29.6°C).
Note: Water temperature between 77°F (25°C) and 84.2°F (29°C) provides warmth and pleasure, making water activities enjoyable for lengthened periods without feeling uncomfortable.

Daylight

The average length of the day in September is 12h and 18min.
On the first day of the month, sunrise is at 7:08 am and sunset at 7:47 pm. On the last day of September, in Sanibel, sunrise is at 7:20 am and sunset at 7:15 pm EDT.

Sunshine

In September, the average sunshine in Sanibel, Florida, is 9.1h.

UV index

The months with the highest UV index in Sanibel are May through September, with an average maximum UV index of 7. A UV Index reading of 6 to 7 represents a high health risk from unprotected exposure to Sun's UV rays for average individuals.
Note: In September, a daily UV index of 7 turns into the following recommendations:
Evade overexposure. Individuals with fair skin risk burning in under 20 minutes. Avoid direct sunlight between the hours of 10 a.m. and 4 p.m., when UV radiation is at its peak. Keep in mind that shade structures may not provide complete protection. Prioritize a wide-brim hat for comprehensive sun defense for your face, neck, eyes, and ears. Take note! Sand and water reflections strengthen the Sun's UV exposure.
Updated: Feb 10, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

How hot is September in Sanibel?

An average high-temperature, in September, in Sanibel, is 86.5°F (30.3°C) and the average low-temperature is 79.2°F (26.2°C). In September, the average heat index (a.k.a. 'feels like', 'apparent temperature'), which combines relative humidity and air temperature, is estimated at 98.6°F (37°C).

What is the average humidity in September in Sanibel?

In September, the average relative humidity is 75%.

How much does it rain in Sanibel in September?

In Sanibel, Florida, in September, during 25.3 rainfall days, 6.18" (157mm) of precipitation is typically accumulated.

How warm is the water in September in Sanibel?

In September, the average ocean temperature in Sanibel is 85.3°F (29.6°C). Water temperature between 77°F (25°C) and 84.2°F (29°C) is regarded as very warm and enjoyable by all. With these temperatures, water activities are pleasurable, without feeling uncomfortable for prolonged periods.

What is the average length of the day in September in Sanibel?

In Sanibel, Florida, the average day length in September is 12h and 18min.

When are sunrise and sunset in September in Sanibel?

In September, on the first day of the month, sunrise is at 7:08 am and sunset at 7:47 pm. On the last day of the month, in Sanibel, Florida, sunrise is at 7:20 am and sunset at 7:15 pm EDT.

How many hours of sunshine does Sanibel have in September?

In September, the average sunshine duration is 9.1h.

When is the highest UV index in Sanibel?

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

What is the UV index reading in September in Sanibel?

In September, the average daily maximum UV index in Sanibel, Florida, is 7. A UV Index value of 6 to 7 symbolizes a high health risk from exposure to Sun's UV rays.

Average temperature in September
Sanibel, FL

Average temperature in September - Sanibel, FL
  • Average high temperature in September: 86.5°F

The warmest month (with the highest average high temperature) is August (88°F).
The month with the lowest average high temperature is January (69.8°F).

  • Average low temperature in September: 79.2°F

The month with the highest average low temperature is August (81.1°F).
The coldest month (with the lowest average low temperature) is January (59.5°F).

Average pressure in September
Sanibel, FL

Average pressure in September - Sanibel, FL
  • Average pressure in September: 29.95"Hg

The month with the highest atmospheric pressure is January (30.11"Hg).
The month with the lowest atmospheric pressure is September (29.95"Hg).

Average wind speed in September
Sanibel, FL

Average wind speed in September - Sanibel, FL
  • Average wind speed in September: 7.9mph

The windiest months (with the highest average wind speed) are October and November (10.1mph).
The calmest month (with the lowest average wind speed) is July (6.9mph).

Average humidity in September
Sanibel, FL

Average humidity in September - Sanibel, FL
  • Average humidity in September: 75%

The month with the highest relative humidity is December (77%).
The months with the lowest relative humidity are March, May, July, August and October (73%).

Average rainfall in September
Sanibel, FL

Average rainfall in September - Sanibel, FL
  • Average rainfall in September: 6.18"

The wettest month (with the highest rainfall) is August (8.54").
The driest month (with the least rainfall) is February (1.06").

Average rainfall days in September
Sanibel, FL

Average rainfall days in September - Sanibel, FL
  • Average rainfall days in September: 25.3 days

The month with the highest number of rainy days is August (27.3 days).
The month with the least rainy days is February (8.2 days).

Average sea temperature in September
Sanibel, FL

Average sea temperature in September - Sanibel, FL
  • Average sea temperature in September: 85.4°F

The best month for swimming (with the highest average sea temperature) is August (87.1°F).
The coldest month (with the lowest average sea temperature) is January (65.3°F).

Average daylight in September /
Average sunshine in September
Sanibel, FL

Average daylight in September / Average sunshine in September - Sanibel, FL
  • Average daylight in September: 12h and 2min

The month with the longest days is June (Average daylight: 13h and 48min).
The month with the shortest days is December (Average daylight: 10h and 30min).

  • Average sunshine in September: 9h and 1min

The month with the most sunshine is May (Average sunshine: 11h and 0min).
The month with the least sunshine is December (Average sunshine: 6h and 36min).

Average sunshine days in September
Sanibel, FL

Average sunshine days in September - Sanibel, FL
  • Average sunshine days in September: 3 days

The month with the most sunshine days is January (19.8 days).
The month with the least sunshine days is August (2.3 days).

Average UV index in September
Sanibel, FL

Average UV index in September - Sanibel, FL
  • 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 February (UV index 5).

Average cloud cover in September
Sanibel, FL

Average cloud cover in September - Sanibel, FL
  • Average cloud cover in September: 28

The month with the most cloud cover is January (Cloud cover 29).
The months with the least cloud cover are March and May (Cloud cover 23).

Average visibility in September
Sanibel, FL

Average visibility in September - Sanibel, FL
  • 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).

Sanibel, Florida, USA

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