September weather forecast
Captiva, FL

September marks the zenith of rainfall in Captiva with 1.02" (26mm). The month sees a slight dip in temperature to 86.7°F (30.4°C), but the rainfall brings relief to the summer blaze. Concurrently, daylight and sunshine duration decelerate. As the summer begins to fade, the weather shifts, creating a captivating blend of warmth and rain.

Temperature

September brings an average high-temperature of a still hot 86.7°F (30.4°C), showing a slight difference from August's 88°F (31.1°C). Captiva records a consistent average nighttime temperature of 79°F (26.1°C) in September, slightly lower than the daytime high.

Heat index

The heat index for September is computed to be a very hot 98.6°F (37°C). Take extra safety measures to prevent heat exhaustion and heat cramps. Heatstroke could follow lengthy activity.
Evaluating the heat index requires understanding its values in the shade and with gentle winds. A rise of up to 15 Fahrenheit (8 Celsius) degrees in the heat index could result from direct sunlight.
Note: The heat index, also known as 'felt air temperature' or 'apparent temperature', stands as a testimony to how temperature and humidity combine to impact our sense of warmth. A person's impression of weather can be shaped by many aspects, among them metabolic variations, pregnancy, and levels of physical activity. The sun, when shining directly, can have a significant impact on the perceived temperature, increasing the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly relevant to babies and toddlers. Children often overlook the need for breaks and fluid intake. Thirst is a late-stage sign of dehydration - hence, it is necessary to stay hydrated, especially during extended periods of physical activities.
The natural method the human body uses to remove excess heat is by perspiring and letting sweat evaporate. During high air temperature and humidity (high heat index), the process of perspiration is hindered, intensifying the sensation of heat. When heat surpasses the body's release mechanisms, dehydration and overheating risks become pronounced.

Humidity

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

Rainfall

In Captiva, during September, the rain falls for 19.5 days and regularly aggregates up to 1.02" (26mm) of precipitation. Throughout the year, there are 122 rainfall days, and 8.98" (228mm) of precipitation is accumulated.

Ocean temperature

In Captiva, the average seawater temperature in September is 84.2°F (29°C).
Note: Water temperature from 77°F (25°C) to 84.2°F (29°C) is considered very warm, making water activities enjoyable for prolonged periods without any uncomfortable sensations.

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 7:48 pm. On the last day of September, sunrise is at 7:21 am and sunset at 7:15 pm EDT.

Sunshine

In September, the average sunshine is 9.1h.

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 threat to health from exposure to the Sun's UV radiation for the ordinary person.
Note: A daily maximum UV index of 7 in September translates into the following instructions:
Undertake protective measures and comply with sun safety rules. Shielding against skin and eye damage is essential. The time between 10 a.m. and 4 p.m. is when UV radiation is at its peak. Limit exposure to direct sunlight during these hours. Sun protection is enhanced with clothing that boasts a tight weave yet offers a loose fit. Caution! Sand and water surfaces escalate the UV intensity from the Sun.