September weather forecast
Key Largo, FL

Key Largo moves towards fall in September, experiencing a slight dip in temperatures compared to August. However, the weather remains largely warm, keeping up the tropical vibes of the island city. Daylight hours start decreasing, yet the sea maintains its warmth, owing to the summer's residual heat. The frequency of rainfall begins to taper off by the end of this month. Temperatures hit a peak of 84.6°F (29.2°C) in September, and rainfall measures approximately 4.25" (108mm).

Temperature

Key Largo's average high-temperature in September is a still moderately hot 84.6°F (29.2°C), marking an insignificant difference from the 85.5°F (29.7°C) of August. Key Largo in September experiences a minor decline in temperature, with an average low of 81.7°F (27.6°C) at night.

Heat index

The heat index in September is estimated at a tropical 93.2°F (34°C). Take special precautions - heat exhaustion and heat cramps are expected. Heatstroke may occur with lengthy activity.
From a standpoint of the heat index, values pertain to shaded conditions and mild breezes. Direct sunlight might cause an increase of up to 15 Fahrenheit (8 Celsius) degrees in the heat index.
Note: The heat index, also known as 'real feel' or 'apparent temperature', provides an understanding of perceived warmth by combining temperature and relative humidity. Metabolic differences, pregnancy status, and the level of physical activity are additional factors influencing an individual's weather perception. Consider that direct sun exposure can intensify the felt heat, adding potentially 15 Fahrenheit (8 Celsius) degrees to the heat index. Heat index values remain especially vital for babies and toddlers. Young children typically face greater hazards than adults because they do not sweat as much. Their larger skin surface in comparison to their little bodies and the high heat production from their active nature compounds their vulnerability.

Humidity

The average relative humidity in September is 74%.

Rainfall

In September, the rain falls for 22.9 days. Throughout September, 4.25" (108mm) of precipitation is accumulated. In Key Largo, during the entire year, the rain falls for 190.1 days and collects up to 27.05" (687mm) of precipitation.

Ocean temperature

In September, the average ocean temperature is 85.6°F (29.8°C).
Note: For any water activity, having surface water temperatures from 77°F (25°C) to 84.2°F (29°C) is considered outstanding and highly delightful for lengthened periods.

Daylight

In September, the average length of the day is 12h and 17min.
On the first day of the month, sunrise is at 7:02 am and sunset at 7:40 pm. On the last day of September, sunrise is at 7:13 am and sunset at 7:09 pm EDT.

Sunshine

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

UV index

April through October, with an average maximum UV index of 7, are months with the highest UV index. A UV Index estimate of 6 to 7 represents a high health vulnerability from unsafe exposure to UV radiation for average individuals.
Note: A maximum high daily UV index of 7 during September translates into the following directions:
Guard against overexposure. Protection from sun-induced harm is essential. Limit direct sun exposure and seek shade between 10 a.m. and 4 p.m., the time of the most intense UV radiation, noting that shade structures may not provide total sun protection. Loose clothes with a tight weave are optimal for safeguarding yourself against the Sun's rays. Caution! The reflection of sand and water significantly amplifies the Sun's UV radiation.