September weather forecast
Sanibel, FL

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.