September weather forecast
Jacksonville, FL

As September comes around, Jacksonville experiences a gradual transition from summer towards fall. There is a noticeable drop in the sea temperature from 83.5°F (28.6°C) in August to 82.9°F (28.3°C). Despite the transition period, the vibrancy of Jacksonville's weather persists. The daylight hours gradually reduce, simplifying the shift towards the cozier latter months of the year. Nevertheless, the temperatures and relative humidity remain considerably high, still echoing summer resonance.

Temperature

In September, Jacksonville notes an average high-temperature of a still hot 86.9°F (30.5°C), hardly different from the preceding month. An average low-temperature of 73.8°F (23.2°C) is observed during the September nights.

Heat index

For most parts of September, the heat index is evaluated at a fiery hot 100.4°F (38°C). Preventive measures are required to mitigate the risk of heat cramps and heat exhaustion. Continuous activity may precipitate heatstroke.
Heat index readings emphasize conditions of light breezes and shaded spots. Direct sunlight might lead to a heat index increase by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'real feel', is derived by integrating air temperature with the existing relative humidity to express the perceived warmth. Elements such as metabolic variations, pregnancy, and physical exertion can shape one's weather perception. By being directly under the sun, it's possible for the felt temperature to increase by 15 Fahrenheit (8 Celsius) degrees. Heat index values are highly critical to babies and toddlers. Young children are more at risk than adults since they tend to sweat less. Moreover, their large skin surface in proportion to their small bodies and the high heat production due to their activities contribute to their vulnerability.
The body's innate mechanism to counteract overheating is through perspiration, as it leverages the cooling effects of sweat evaporation. Higher relative humidity impedes evaporation, thus reducing heat dispersion from the body, culminating in a sensation of overheating. When body temperature rises due to excess heat gain beyond its removal capability, one might experience heat-related disorders.

Humidity

In September, the average relative humidity is 75%.

Rainfall

In September, the rain falls for 18.5 days. Throughout September, 2.48" (63mm) of precipitation is accumulated. In Jacksonville, Florida, during the entire year, the rain falls for 172.6 days and collects up to 25.35" (644mm) of precipitation.

Snowfall

In Jacksonville, snow does not fall in January through November.

Ocean temperature

In September, the average ocean temperature is 82.9°F (28.3°C).
Note: Ideal surface water temperatures for any water activity fall between 77°F (25°C) and 84.2°F (29°C), offering maximum enjoyment for lengthened periods.

Daylight

In September, the average length of the day is 12h and 20min.
On the first day of September, sunrise is at 7:03 am and sunset at 7:49 pm. On the last day of the month, sunrise is at 7:19 am and sunset at 7:12 pm EDT.

Sunshine

In September, the average sunshine is 8.5h.

UV index

In Jacksonville, the average daily maximum UV index in September is 6. A UV Index value of 6 to 7 symbolizes a high threat to health from unsafe exposure to UV radiation for average individuals.
Note: A maximum daily UV index of 6 during September morphs into the following directions:
Take precautions and adopt sun safety practices. Protection against sunburn is obliged. Stay in the shade and avoid direct Sun exposure from 10 a.m. to 4 p.m., a time when UV radiation is at its strongest, and remember that parasols or canopies do not offer full protection. For holistic sun protection encompassing the eyes, ears, face, and neck, a wide-brim hat is key. Be vigilant! The Sun's UV rays get a boost from sand and water reflections.