Average Weather in May in Key West Florida, United States
In Key West, the month of May is characterized by gradually rising daily high temperatures, with daily highs increasing by 3°F, from 83°F to 86°F over the course of the month, and rarely exceeding 88°F or dropping below 79°F.
Daily low temperatures increase by 4°F, from 75°F to 78°F, rarely falling below 70°F or exceeding 81°F.
For reference, on August 7, the hottest day of the year, temperatures in Key West typically range from 81°F to 89°F, while on January 18, the coldest day of the year, they range from 65°F to 74°F.
Average High and Low Temperature in May
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on May. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.
Average Hourly Temperature in May
The month of May in Key West experiences very rapidly increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 35% to 57%.
The clearest day of the month is May 1, with clear, mostly clear, or partly cloudy conditions 65% of the time.
For reference, on June 20, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 70%, while on March 6, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 73%.
Cloud Cover in May
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Key West, the chance of a wet day over the course of May is very rapidly increasing, starting the month at 17% and ending it at 44%.
For reference, the year's highest daily chance of a wet day is 59% on September 16, and its lowest chance is 12% on March 20.
Probability of Precipitation in May
To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.
The average sliding 31-day rainfall during May in Key West is very rapidly increasing, starting the month at 2.3 inches, when it rarely exceeds 5.4 inches or falls below 0.3 inches, and ending the month at 5.1 inches, when it rarely exceeds 10.5 inches or falls below 1.4 inches.
Average Monthly Rainfall in May
Over the course of May in Key West, the length of the day is gradually increasing. From the start to the end of the month, the length of the day increases by 28 minutes, implying an average daily increase of 57 seconds, and weekly increase of 6 minutes, 36 seconds.
The shortest day of the month is May 1, with 13 hours, 5 minutes of daylight and the longest day is May 31, with 13 hours, 33 minutes of daylight.
Hours of Daylight and Twilight in May
The latest sunrise of the month in Key West is 6:51 AM on May 1 and the earliest sunrise is 13 minutes earlier at 6:38 AM on May 31.
The earliest sunset is 7:56 PM on May 1 and the latest sunset is 15 minutes later at 8:11 PM on May 31.
Daylight saving time is observed in Key West during 2017, but it neither starts nor ends during May, so the entire month is in daylight saving time.
For reference, on June 21, the longest day of the year, the Sun rises at 6:39 AM and sets 13 hours, 40 minutes later, at 8:18 PM, while on December 21, the shortest day of the year, it rises at 7:06 AM and sets 10 hours, 37 minutes later, at 5:43 PM.
Sunrise & Sunset with Twilight in May
We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.
The chance that a given day will be muggy in Key West is very rapidly increasing during May, rising from 74% to 97% over the course of the month.
For reference, on July 3, the muggiest day of the year, there are muggy conditions 100% of the time, while on January 29, the leasy muggy day of the year, there are muggy conditions 42% of the time.
Humidity Comfort Levels in May
This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.
The average hourly wind speed in Key West is gradually decreasing during May, decreasing from 6.5 miles per hour to 5.8 miles per hour over the course of the month.
For reference, on November 7, the windiest day of the year, the daily average wind speed is 7.9 miles per hour, while on July 29, the calmest day of the year, the daily average wind speed is 5.0 miles per hour.
Average Wind Speed in May
Wind Direction in May
Key West is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.
The average surface water temperature in Key West is gradually increasing during May, rising by 3°F, from 79°F to 82°F, over the course of the month.
Average Water Temperature in May
This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.
The average daily incident shortwave solar energy in Key West is decreasing during May, falling by 1.1 kWh, from 6.9 kWh to 5.8 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in May
For the purposes of this report, the geographical coordinates of Key West are 24.555 deg latitude, -81.782 deg longitude, and 0 ft elevation.
The topography within 2 miles of Key West is essentially flat, with a maximum elevation change of 10 feet and an average elevation above sea level of 2 foot. Within 10 miles is also essentially flat (10 feet). Within 50 miles is also essentially flat (16 feet).
The area within 2 miles of Key West is covered by water (59%) and artificial surfaces (37%), within 10 miles by water (95%), and within 50 miles by water (99%).
This report illustrates the typical weather in Key West year round, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.
Temperature and Dew Point
There is only a single weather station, Key West International Airport, in our network suitable to be used as a proxy for the historical temperature and dew point records of Key West.
At a distance of 3 kilometers from Key West, closer than our threshold of 150 kilometers, this station is deemed sufficiently nearby to be relied upon as our primary source for temperature and dew point records.
The station records are corrected for the elevation difference between the station and Key West according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
Please note that the station records themselves may additionally have been back-filled using other nearby stations or the MERRA-2 reanalysis.
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , by Jean Meeus.
All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.
Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.
Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.
Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .
Time zones for aiports and weather stations are provided by AskGeo.com .
Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.