September weather forecast
Dismal Key, FL

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Weather in September

The first month of the autumn, September, is still a hot month in Dismal Key, Florida, with temperature in the range of an average low of 78.4°F (25.8°C) and an average high of 87.1°F (30.6°C).

Temperature

September's average high-temperature stands at a still hot 87.1°F (30.6°C), showing little deviation from August's 88.3°F (31.3°C). Dismal Key welcomes an average low temperature of 78.4°F (25.8°C) in September, a gentle shift from the day's high.

Heat index

The heat index value during September is computed to be a torrid 100.4°F (38°C). Preventive measures are required to mitigate the risk of heat cramps and heat exhaustion. Continuous activity may precipitate heatstroke.
The heat index's values are generally associated with conditions in shade and light breezes. The heat index could experience an increase of 15 Fahrenheit (8 Celsius) degrees due to direct sunlight.
Note: The heat index, also known as 'feels like' or 'real feel', stands as a testimony to how temperature and humidity combine to impact our sense of warmth. 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 hold great significance to children. Youngsters generally face more threats than adults given their lesser ability to sweat. Coupled with their larger skin surface relative to their small bodies and higher heat production due to their activities, they are more endangered.
In the face of high temperatures, the human body's reflex is to perspire, leveraging sweat evaporation for cooling. When the relative humidity is high, the evaporation rate is reduced. The warmth is removed from the body at a lower rate, causing the body to retain more heat than it would in dry air. Overheating and potential dehydration arise when body heat gain eclipses its release capability.

Humidity

The average relative humidity in September is 75%.

Rainfall

In Dismal Key, during September, the rain falls for 21.5 days and regularly aggregates up to 2.4" (61mm) of precipitation. Throughout the year, there are 162.1 rainfall days, and 21.69" (551mm) of precipitation is accumulated.

Daylight

In September, the average length of the day is 12h and 18min.
On the first day of September, sunrise is at 7:06 am and sunset at 7:45 pm. On the last day of the month, sunrise is at 7:18 am and sunset at 7:13 pm EDT.

Sunshine

The average sunshine in September is 9.2h.

UV index

The months with the highest UV index are May through September, with an average maximum UV index of 7. A UV Index value of 6 to 7 symbolizes a high health vulnerability from exposure to the Sun's UV rays for the average person.
Note: The UV index of 7 during September translates into the following guidance:
Embrace precautions and observe sun safety norms. Evasion of sunburn is a necessity. Between 10 a.m. and 4 p.m., the Sun's UV radiation is at its peak. Limit your exposure to direct sunlight during these hours. Outfit yourself in sun-safe attire, like long sleeves, pants, a hat, and UV-blocking sunglasses.
Updated: Jun 29, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

How hot is September?

September temperatures in Dismal Key vary between a high-temperature of 87.1°F (30.6°C) and a low-temperature of 78.4°F (25.8°C). In September, the average heat index (a.k.a. 'felt air temperature', 'real feel'), which calculates the temperature value influenced by the moisture in the air, is computed to be 100.4°F (38°C).

What is the average humidity in September?

The average relative humidity in September is 75%.

How many days does it rain in September?

In Dismal Key, in September, during 21.5 rainfall days, 2.4" (61mm) of precipitation is typically accumulated.

How many hours of daylight does Dismal Key have in September?

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

When are sunrise and sunset in September?

In September, on the first day of the month, sunrise is at 7:06 am and sunset at 7:45 pm. On the last day of the month, sunrise is at 7:18 am and sunset at 7:13 pm EDT.

How long on average sun shines in September?

In Dismal Key, the average sunshine duration in September is 9.2h.

What is the month with the highest UV index?

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

What is the UV index intensity in September?

In September, the average daily maximum UV index is 7. A UV Index value of 6 to 7 symbolizes a high health risk from exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Dismal Key, FL

Average temperature in September - Dismal Key, FL
  • Average high temperature in September: 87.1°F

The warmest month (with the highest average high temperature) is August (88.3°F).
The month with the lowest average high temperature is January (71.6°F).

  • Average low temperature in September: 78.4°F

The month with the highest average low temperature is August (80.2°F).
The coldest month (with the lowest average low temperature) is January (59.5°F).

Average pressure in September
Dismal Key, FL

Average pressure in September - Dismal Key, FL
  • Average pressure in September: 29.94"Hg

The month with the highest atmospheric pressure is January (30.11"Hg).
The month with the lowest atmospheric pressure is September (29.94"Hg).

Average wind speed in September
Dismal Key, FL

Average wind speed in September - Dismal Key, FL
  • Average wind speed in September: 7mph

The windiest month (with the highest average wind speed) is November (9.2mph).
The calmest month (with the lowest average wind speed) is July (6.2mph).

Average humidity in September
Dismal Key, FL

Average humidity in September - Dismal Key, FL
  • Average humidity in September: 75%

The month with the highest relative humidity is December (76%).
The month with the lowest relative humidity is March (72%).

Average rainfall in September
Dismal Key, FL

Average rainfall in September - Dismal Key, FL
  • Average rainfall in September: 2.4"

The wettest month (with the highest rainfall) is August (4.29").
The driest month (with the least rainfall) is March (0.63").

Average rainfall days in September
Dismal Key, FL

Average rainfall days in September - Dismal Key, FL
  • Average rainfall days in September: 21.5 days

The month with the highest number of rainy days is August (22.4 days).
The month with the least rainy days is February (7 days).

Average daylight in September /
Average sunshine in September
Dismal Key, FL

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

The month with the longest days is June (Average daylight: 13h and 42min).
The month with the shortest days is December (Average daylight: 10h and 36min).

  • Average sunshine in September: 9h and 1min

The months with the most sunshine are May and July (Average sunshine: 11h and 6min).
The month with the least sunshine is December (Average sunshine: 6h and 42min).

Average sunshine days in September
Dismal Key, FL

Average sunshine days in September - Dismal Key, FL
  • Average sunshine days in September: 7.1 days

The month with the most sunshine days is January (21.8 days).
The month with the least sunshine days is August (6.8 days).

Average UV index in September
Dismal Key, FL

Average UV index in September - Dismal Key, 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
Dismal Key, FL

Average cloud cover in September - Dismal Key, FL
  • Average cloud cover in September: 27

The month with the most cloud cover is January (Cloud cover 28).
The months with the least cloud cover are March and April (Cloud cover 22).

Average visibility in September
Dismal Key, FL

Average visibility in September - Dismal Key, 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).

Dismal Key, Florida, USA

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