Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average sea temperature in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
Key West's weather in September, with an average high-temperature of a still warm 84.4°F, subtly shifts from August's 85.3°F. A slight dip in temperature to a still moderately hot 82.2°F marks the average nights in Key West during September.Heat index
September's heat index is estimated at a hot 93.2°F. Exercise enhanced safety steps, heat cramps and heat exhaustion are probable. Heatstroke could be a result of sustained activity.Given the heat index, its values are aligned with shaded sites and gentle winds. The heat index could see an increase by 15 Fahrenheit (8 Celsius) degrees under direct sunshine.
Note: The heat index, also known as 'real feel' or 'felt air temperature', ties air temperature with relative humidity to produce the perceived temperature sensation. The effect is personal, with varied weather perceptions among individuals due to differences in body mass, stature, and physical activity. Taking into account that direct sunlight can boost the heat effect, the heat index may rise by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values remain especially vital for babies and toddlers. Young individuals are typically more threatened than adults due to their reduced perspiration. Also, the larger skin surface proportionate to their small bodies and the increased heat from their activities magnify their risk.
Humidity
July through September, with an average relative humidity of 74%, are the least humid months.Rainfall
September is the month with the most rainfall in Key West. Rain falls for 23.1 days and accumulates 5.12" of precipitation.Ocean temperature
In Key West, the average seawater temperature in September is 85.6°F.Note: In water temperatures ranging between 77°F and 84.2°F, activities such as swimming and diving become highly pleasurable for long durations.
Daylight
In September, the average length of the day is 12h and 17min.On the first day of September in Key West, Florida, sunrise is at 7:08 am and sunset at 7:45 pm. On the last day of the month, sunrise is at 7:18 am and sunset at 7:15 pm EDT.
Sunshine
In September, the average sunshine in Key West, Florida, 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 value of 6 to 7 symbolizes a high health vulnerability from exposure to the Sun's UV radiation for average individuals.Note: A typical high UV index of 7 in September suggests the following recommendations:
Shield from overexposure. Defense against sun-related harm is required. The Sun emits the most powerful UV radiation between 10 a.m. and 4 p.m. Try to avoid direct sunlight during this period. A wide-brim hat offers excellent sun protection for the eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Caution! The reflection of sand and water significantly increases the intensity of the Sun's UV radiation.
FAQ
How hot is September in Key West?
What are the least humid months in Key West?
What is the average humidity in September in Key West?
What is the rainiest month in Key West?
How much does it rain in Key West in September?
What is the water temperature in September in Key West?
How many hours of daylight does Key West have in September?
When are sunrise and sunset in September in Key West?
How long on average sun shines in September in Key West?
What are the months with the highest UV index in Key West?
What is the UV index reading in September in Key West?
Average temperature in September
Key West, FL
- Average high temperature in September: 84.4°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 September: 82.2°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).
Average pressure in September
Key West, FL
- Average pressure in September: 29.93"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).
Average wind speed in September
Key West, FL
- Average wind speed in September: 10.3mph
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).
Average humidity in September
Key West, FL
- Average humidity in September: 74%
The month with the highest relative humidity is February (78%).
The months with the lowest relative humidity are July, August and September (74%).
Average rainfall in September
Key West, FL
- Average rainfall in September: 5.12"
The wettest month (with the highest rainfall) is September (5.12").
The driest month (with the least rainfall) is March (0.67").
Average rainfall days in September
Key West, FL
- Average rainfall days in September: 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).
Average sea temperature in September
Key West, FL
- Average sea temperature in September: 85.6°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).
Average daylight in September /
Average sunshine in September
Key West, FL
- Average daylight in September: 12h and 2min
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 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 18min).
Average sunshine days in September
Key West, FL
- Average sunshine days in September: 4.5 days
The month with the most sunshine days is March (17 days).
The month with the least sunshine days is September (4.5 days).
Average UV index in September
Key West, 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).
Average cloud cover in September
Key West, FL
- Average cloud cover in September: 29
The month with the most cloud cover is January (Cloud cover 34).
The month with the least cloud cover is April (Cloud cover 23).
Average visibility in September
Key West, 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).
Key West, Florida, USA
Weather forecast for your location
2. Allow the app to use your location
