September weather forecast and climate
Key West, FL

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
September is the worst month to visit Key West with the hurricane season at its peak. It is the wettest month of the year with 6.7" (170.2mm) of rainfall and prone to storms and floods. Key West hosts mainly the local population during September. Average high temperatures drop a little to an average of 87°F (30.6°C) in September, and the skies are partly cloudy.
The Ernest Hemingway Home and Museum, located in the Old Town, is an exciting place to spend a rainy day.

What is the average temperature in September in Key West?

The average high-temperature, in September, in Key West, is 88°F (31.1°C), while the average low-temperature is 78.4°F (25.8°C).
Average temperature in September - Key West, FL
  • Average high temperature in September: 87.9°F

The warmest month (with the highest average high temperature) is August (89.4°F).
The month with the lowest average high temperature is January (74.3°F).

  • Average low temperature in September: 78.5°F

The month with the highest average low temperature is July (79.8°F).
The coldest month (with the lowest average low temperature) is January (64.2°F).

Average humidity in September - Key West, FL
  • Average humidity in September: 75.3%

The month with the highest relative humidity is December (76.2%).
The month with the lowest relative humidity is April (70.1%).

Average rainfall in September - Key West, FL
  • Average rainfall in September: 6.5"

The wettest month (with the highest rainfall) is September (6.5").
The driest month (with the lowest rainfall) is March (1.6").

Average rainfall days in September - Key West, FL
  • Average rainfall days in September: 16.2 days

The month with the highest number of rainy days is September (16.2 days).
The month with the lowest number of rainy days is April (4.5 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).
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: 12.3h

The month with the longest days is June (Average daylight: 13.6h).
The month with shortest days is December (Average daylight: 10.6h).

  • Average sunshine in September: 9h

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

Average UV index in September - Key West, FL
  • Average UV index in September: 10

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

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