Key West
Florida, USA
Long term weather forecast
Long term weather forecast

September weather forecast and Climate
Key West, FL

  • Average high temperature in September: 87.9°F

Warmest month (with highest average high temperature) is August (89.4°F).
Month with lowest average high temperature is January (74.3°F).

  • Average low temperature in September: 78.5°F

Month with highest average low temperature is July (79.8°F).
Coldest month (with lowest average low temperature) is January (64.2°F).

  • Average humidity in September: 75.3%

Month with highest relative humidity is December (76.2%).
Month with lowest relative humidity is April (70.1%).

  • Average rainfall in September: 6.5"

Wettest month (with highest rainfall) is September (6.5").
Driest month (with lowest rainfall) is March (1.6").

  • Average rainfall days in September: 16.2 days

Month with highest number of rainy days is September (16.2 days).
Month with lowest number of rainy days is April (4.5 days).

  • Average sea temperature in September: 84°F

Best month for swimming (with highest average sea temperature) is August (86°F).
Coldest months (with lowest average sea temperature) are January, February and March (75°F).

  • Average daylight in September: 12h

Month with longest days is June (Average daylight: 14h).
Months with shortest days are January, February, November and December (Average daylight: 11h).

  • Average sunshine in September: 9h

Month with most sunshine is May (Average sunshine: 11h).
Month with least sunshine is December (Average sunshine: 7.6h).

  • Average UV index in September: 10

Months with highest UV index are April, May, June, July and August (UV index 11).
Months with lowest UV index are January and December (UV index 6).

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