September weather forecast
Key Largo, FL

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A clear seascape and cloudy evening sky in Key Largo, Florida
A clear seascape and cloudy evening sky in Key Largo, Florida

Weather in September

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

September in Key Largo is marked by an average high-temperature of a still warm 84.6°F (29.2°C), almost identical to the preceding month. Nighttime temperature sees a small decrement from daytime highs, dipping to an average of 81.7°F (27.6°C) during September.

Heat index

During September, the heat index is estimated at a hot 93.2°F (34°C). Incorporate special precautions, risk of heat exhaustion and heat cramps is substantial. Sustained activity could cause heatstroke.
Heat index specifics point out values are for conditions of shade and a slight breeze. Direct sunlight has the potential to heighten heat index values by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'felt air temperature' or 'real feel', shows a temperature sensation when both heat and moisture conditions are combined. The impact of weather is individual, with diverse individuals experiencing it differently due to variations in body mass, height, and activity levels. Being under direct sunshine can magnify the heat experience, possibly pushing up the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are highly important for children. Kids often lack the knowledge about the necessity to take breaks and consume liquids. Thirst, as a late symptom of dehydration, necessitates the maintenance of hydration, particularly during enduring physical activities.

Humidity

In Key Largo, the average relative humidity in September is 74%.

Rainfall

In Key Largo, in September, it is raining for 22.9 days, with typically 4.25" (108mm) of accumulated precipitation. 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 Key Largo, the average seawater temperature in September is 85.6°F (29.8°C).
Note: Water temperature ranging from 77°F (25°C) to 84.2°F (29°C) is recognized as warm and pleasant by all, making water activities comfortable and delightful for long durations.

Daylight

The average length of the day in September 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, in Key Largo, Florida, sunrise is at 7:13 am and sunset at 7:09 pm EDT.

Sunshine

The average sunshine in September in Key Largo is 9h.

UV index

The months with the highest UV index are April through October, with an average maximum UV index of 7. A UV Index reading of 6 to 7 represents a high threat to health from unsafe exposure to UV radiation for ordinary individuals.
Note: In September, the maximum UV index of 7 transforms into these recommendations:
Escape overexposure. People with light skin may incur burns in fewer than 20 minutes. The Sun's UV radiation is most intense from 10 a.m. to 4 p.m. Try to avoid direct sun exposure during these hours. Clothes that are both tight-knit and comfortably loose are prime choices for sun protection. Be attentive! The UV exposure is heightened with reflections from sand and water.
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Frequently asked questions

How hot is it in Key Largo in September?

The average high-temperature and low-temperature during September are 84.6°F (29.2°C) and 81.7°F (27.6°C) respectively. In September, the average heat index (a.k.a. 'real feel', 'feels like'), which factors the actual air temperature with the relative humidity, is estimated at 93.2°F (34°C).

What is the average humidity in September in Key Largo?

In September, the average relative humidity in Key Largo, Florida, is 74%.

How much does it rain in Key Largo in September?

In Key Largo, Florida, in September, during 22.9 rainfall days, 4.25" (108mm) of precipitation is typically accumulated.

What is the ocean temperature in September in Key Largo?

In Key Largo, the average seawater temperature in September is 85.6°F (29.8°C). For any water activity, surface water temperatures between 77°F (25°C) and 84.2°F (29°C) are considered as excellent and extremely pleasant for lengthened periods.

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

The average day length in September is 12h and 17min.

What time are sunrise and sunset in September in Key Largo?

On the first day of September, sunrise is at 7:02 am and sunset at 7:40 pm. On the last day of the month, sunrise is at 7:13 am and sunset at 7:09 pm EDT.

How long on average sun shines in September in Key Largo?

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

What is the month with the highest UV index in Key Largo?

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

What is the UV index reading in September in Key Largo?

The average daily maximum UV index in September in Key Largo, Florida, is 7. A UV Index estimate of 6 to 7 represents a high hazard to health from exposure to Sun's UV rays.

Average temperature in September
Key Largo, FL

Average temperature in September - Key Largo, FL
  • Average high temperature in September: 84.6°F

The warmest month (with the highest average high temperature) is August (85.5°F).
The month with the lowest average high temperature is January (72.7°F).

  • Average low temperature in September: 81.7°F

The month with the highest average low temperature is August (82.9°F).
The coldest month (with the lowest average low temperature) is January (66.9°F).

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Average pressure in September
Key Largo, FL

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

The month with the highest atmospheric pressure is January (30.1"Hg).
The months with the lowest atmospheric pressure are September and October (29.94"Hg).

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Average wind speed in September
Key Largo, FL

Average wind speed in September - Key Largo, FL
  • Average wind speed in September: 9.4mph

The windiest month (with the highest average wind speed) is January (12.9mph).
The calmest month (with the lowest average wind speed) is July (8.9mph).

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Average humidity in September
Key Largo, FL

Average humidity in September - Key Largo, FL
  • Average humidity in September: 74%

The months with the highest relative humidity are February, June and December (76%).
The month with the lowest relative humidity is March (73%).

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Average rainfall in September
Key Largo, FL

Average rainfall in September - Key Largo, FL
  • Average rainfall in September: 4.25"

The wettest month (with the highest rainfall) is August (4.33").
The driest month (with the least rainfall) is March (0.59").

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Average rainfall days in September
Key Largo, FL

Average rainfall days in September - Key Largo, FL
  • Average rainfall days in September: 22.9 days

The month with the highest number of rainy days is September (22.9 days).
The month with the least rainy days is February (9.7 days).

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Average sea temperature in September
Key Largo, FL

Average sea temperature in September - Key Largo, FL
  • Average sea temperature in September: 85.5°F

The best month for swimming (with the highest average sea temperature) is August (86.5°F).
The coldest month (with the lowest average sea temperature) is February (74°F).

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

Average daylight in September / Average sunshine in September - Key Largo, 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 0min

The month with the most sunshine is July (Average sunshine: 11h and 0min).
The month with the least sunshine is December (Average sunshine: 6h and 24min).

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Average sunshine days in September
Key Largo, FL

Average sunshine days in September - Key Largo, FL
  • Average sunshine days in September: 5.2 days

The month with the most sunshine days is January (17.3 days).
The month with the least sunshine days is September (5.2 days).

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Average UV index in September
Key Largo, FL

Average UV index in September - Key Largo, FL
  • Average UV index in September: 7

The months with the highest UV index are April, May, June, July, August, September and October (UV index 7).
The month with the lowest UV index is January (UV index 5).

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Average cloud cover in September
Key Largo, FL

Average cloud cover in September - Key Largo, FL
  • Average cloud cover in September: 30

The month with the most cloud cover is October (Cloud cover 35).
The month with the least cloud cover is April (Cloud cover 26).

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Average visibility in September
Key Largo, FL

Average visibility in September - Key Largo, 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).

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Key Largo, Florida, USA

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