Key West Weather in September
September's weather is the year's wettest for Key West, Florida. Still, the sun beams down during most of daylight.
This page gives detailed information on the typical September temperature, precipitation, sun, humidity, wind and storms for Key West. The numbers here are historical averages based on climate data gathered at the Key West International Airport, located on Key West Island.
|89 °F||September average high||30 °C|
|79 °F||September average low||26 °C|
|10 days||90 °F max. or more (32 °C)|
|0 days||70 °F min. or less (21 °C)|
Typically every September day at Key West has a temperature of at least 80 degrees Fahrenheit (27 degrees Celsius). Temperatures above 100 °F (38 °C) are not expected here this month.
|7.2 in||total precipitation||184 mm|
|16 days||of rain|
September is the rainiest month for Key West. Half the time, the island receives 5.6 to 8.3 inches (142 to 210 mm) of rainfall in September. One in four years has drier weather, while another one in four is wetter.
|3 days||clear skies|
The sun's rays reach the ground in Key West during 72 percent of daylight hours on average in September, for a total of 265 hours in the month. Typically on 3 days this month the sky is mainly clear, with at most 30 percent cloud cover.
Sunlight in September at Key West lasts for 12 hours and 16 minutes a day on average. The longest day of the month is the 1st with 12 hours and 37 minutes of daylight. By the end of the month, the days have shortened to 11:56 from sunrise to sunset. These durations can vary by a minute or two from year to year.
|75 %||September average humidity|
The relative humidity in Key West during September usually peaks at 81 percent in the morning then drops to 69 percent by early afternoon.
|Local Time||1 am||4 am||7 am||10 am||1 pm||4 pm||7 pm||10 pm||Humidity %||79||80||81||72||70||69||75||77|
|9.5 mph||September wind speed average||15.3 kph|
September is less windy than most other months in Key West.
|4 days||rainfall of 0.5 inches (13 mm) or more|
|12 days||with thunderstorms in September|
|14 %||chance a named storm approaches|
There's a 6 percent probability that a hurricane will approach within 100 miles (165 km) of Key West during September. The chance of a major category 3 to 5 hurricane reaching the area is 2 percent.
The weather data here are long-term averages provided by the US National Centers for Environmental Information (NCEI). Temperature and precipitation are 1991-2020 normals while humidity and thunderstorms are 1961-1990 normals. The named storm probabilities come from the Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division.