August weather forecast
Key West, FL

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A beach pier in Key West, Florida, with palm trees in the background
A beach pier in Key West, Florida, with palm trees in the background

Weather in August

August can be deemed as the most active month in terms of weather events in Key West. The intensity of sunlight during day time is counteracted by the occasional thunderstorms which bring respite from the heat. The constant weather changes can sometimes result in unfavorable conditions, but the tropical charm of the city remains intact. Along with the peak of hurricane season, the month offers the highest sea temperatures, peaking at 86.9°F, defining August's marine appeal.

Temperature

August temperatures tend to peak at an average high of 85.3°F and dip to a low of 82.9°F.

Heat index

Throughout August, the heat index is estimated at a torrid 95°F. Preventive measures are required to mitigate the risk of heat cramps and heat exhaustion. Continuous activity may precipitate heatstroke.
Consider that heat index readings are for situations in the shade and light wind. The direct sun can potentially cause the heat index to increase by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'apparent temperature', combines both the air temperature and the humidity level to give a perceived human temperature. One's weather perception can be influenced by a range of factors including metabolic differences, being pregnant, and their level of physical activity. In direct sunlight, the heat's impact can be heightened, potentially leading to an increase in the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are quite important for children. Young people are generally more susceptible than adults because they perspire less. Furthermore, their proportionally larger skin surface to their petite bodies and the increased heat output from their actions add to the risk.
Perspiration, followed by sweat evaporation, is the human body's chief method to maintain a balanced temperature. Under high air temperature and high humidity (high heat index) conditions, the body's ability to perspire is compromised, increasing the sensation of heat. Should the body fail to balance its heat gain, the escalating temperature poses health challenges.

Humidity

The months with the lowest humidity are July through September, with an average relative humidity of 74%.

Rainfall

In August, the rain falls for 23.1 days. Throughout August, 4.33" of precipitation is accumulated. Throughout the year, there are 199.2 rainfall days, and 31.61" of precipitation is accumulated.

Ocean temperature

August is the month with the warmest seawater, with an average ocean temperature of 86.9°F.
Note: When water's temperature exceeds 86°F, it arguably loses its primary appeal of offering a cool escape.

Daylight

In Key West, the average length of the day in August is 12h and 58min.
On the first day of August in Key West, sunrise is at 6:55 am and sunset at 8:11 pm. On the last day of the month, sunrise is at 7:07 am and sunset at 7:46 pm EDT.

Sunshine

The average sunshine in August is 9.7h.

UV index

April through October, with an average maximum UV index of 7, are months with the highest UV index in Key West. A UV Index value of 6 to 7 symbolizes a high health hazard from exposure to the Sun's UV rays for average individuals.
Note: An average UV index of 7 in August transforms into this advice:
Inhibit overexposure. Warding off sun damage is of utmost importance. The Sun's UV radiation is most potent between 10 a.m. and 4 p.m. Try to limit direct exposure to the Sun during this period. Always opt for UVA and UVB-resistant sunglasses on radiant days. Warning! The reflection of sand and water increases the UV dose.
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FAQ

What is the warmest month in Key West?

In Key West, Florida, the average highest temperatures are observed in August, with a high of 85.3°F and a low of 82.9°F.

How hot does it get in Key West in August?

The high-temperature, in August, in Key West, records 85.3°F, while the low-temperature is 82.9°F. The average heat index (a.k.a. 'felt air temperature', 'real feel'), which combines relative humidity and air temperature, in August is estimated at 95°F.

What is the least humid month in Key West?

The months with the lowest humidity in Key West are July through September, with an average relative humidity of 74%.

What is the average humidity in August in Key West?

In August, the average relative humidity in Key West, Florida, is 74%.

How many days does it rain in August in Key West?

In Key West, in August, it is raining for 23.1 days, with typically 4.33" of accumulated precipitation.

What month is the ocean warmest in Key West?

August is the month with the warmest seawater, with an average ocean temperature of 86.9°F.

How warm is the water in August in Key West?

In Key West, Florida, the average seawater temperature in August is 86.9°F. The water temperature above 86°F is arguably regarded as unpleasant. The primary purpose of entering the water - cooling down from sunshine and high temperatures - is lost.

How many hours of daylight does Key West have in August?

In Key West, the average day length in August is 12h and 58min.

When is the sunrise / sunset in August in Key West?

In August, on the first day of the month, sunrise is at 6:55 am and sunset at 8:11 pm. On the last day of the month, sunrise is at 7:07 am and sunset at 7:46 pm EDT.

How long on average sun shines in August in Key West?

In August, the average sunshine duration is 9.7h.

What are the months with the highest UV index in Key West?

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

What is the UV index intensity in August in Key West?

In August, the average daily maximum UV index is 7. A UV Index of 6 to 7 symbolizes a high health threat from unprotected exposure to UV radiation.
Average high temperature
Average low temperature
Average pressure
Average wind speed
Average max. wind speed
Average wind speed gusts
Average humidity
Average rainfall
Average rainfall days
Average sea temperature
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in August
Key West, FL

Average temperature in August - Key West, FL
  • Average high temperature in August: 85.3°F

The warmest month (with the highest average high temperature) is August (85.3°F).
The month with the lowest average high temperature is January (72.7°F).

  • Average low temperature in August: 82.9°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 (68.5°F).

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Average pressure in August
Key West, FL

Average pressure in August - Key West, FL
  • Average pressure in August: 29.97"Hg

The month with the highest atmospheric pressure is January (30.09"Hg).
The months with the lowest atmospheric pressure are September and October (29.93"Hg).

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Average wind speed in August
Key West, FL

Average wind speed in August - Key West, FL
  • Average wind speed in August: 10.1mph

The windiest months (with the highest average wind speed) are January and November (14.4mph).
The calmest month (with the lowest average wind speed) is July (9.5mph).

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Average humidity in August
Key West, FL

Average humidity in August - Key West, FL
  • Average humidity in August: 74%

The month with the highest relative humidity is February (78%).
The months with the lowest relative humidity are July, August and September (74%).

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Average rainfall in August
Key West, FL

Average rainfall in August - Key West, FL
  • Average rainfall in August: 4.33"

The wettest month (with the highest rainfall) is September (5.12").
The driest month (with the least rainfall) is March (0.67").

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Average rainfall days in August
Key West, FL

Average rainfall days in August - Key West, FL
  • Average rainfall days in August: 23.1 days

The months with the highest number of rainy days are August and September (23.1 days).
The month with the least rainy days is February (11 days).

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Average sea temperature in August
Key West, FL

Average sea temperature in August - Key West, FL
  • Average sea temperature in August: 86.9°F

The best month for swimming (with the highest average sea temperature) is August (86.9°F).
The coldest months (with the lowest average sea temperature) are January and February (71.2°F).

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Average daylight in August /
Average sunshine in August
Key West, FL

Average daylight in August / Average sunshine in August - Key West, FL
  • Average daylight in August: 13h and 0min

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

  • Average sunshine in August: 9h and 4min

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 18min).

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Average sunshine days in August
Key West, FL

Average sunshine days in August - Key West, FL
  • Average sunshine days in August: 6.2 days

The month with the most sunshine days is March (17 days).
The month with the least sunshine days is September (4.5 days).

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Average UV index in August
Key West, FL

Average UV index in August - Key West, FL
  • Average UV index in August: 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 August
Key West, FL

Average cloud cover in August - Key West, FL
  • Average cloud cover in August: 28

The month with the most cloud cover is January (Cloud cover 34).
The month with the least cloud cover is April (Cloud cover 23).

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Average visibility in August
Key West, FL

Average visibility in August - Key West, FL
  • Average visibility in August: 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 West, Florida, USA

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