Climate and Average Weather Year Round in Key West Florida, United States
In Key West, the summers are long, hot, oppressive, wet, and mostly cloudy and the winters are short, comfortable, humid, windy, and mostly clear. Over the course of the year, the temperature typically varies from 65°F to 89°F and is rarely below 56°F or above 91°F.
Based on the beach/pool score, the best times of year to visit Key West for hot-weather activities are from mid March to mid May and from late October to late November.
Climate in Key West
The hot season lasts for 4.0 months, from June 2 to October 2, with an average daily high temperature above 86°F. The hottest month of the year in Key West is August, with an average high of 89°F and low of 81°F.
The cool season lasts for 3.0 months, from December 7 to March 6, with an average daily high temperature below 77°F. The coldest month of the year in Key West is January, with an average low of 66°F and high of 74°F.
Average High and Low Temperature in Key West
The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, 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 Key West
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
In Key West, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year in Key West begins around October 19 and lasts for 7.1 months, ending around May 23.
The clearest month of the year in Key West is February, during which on average the sky is clear, mostly clear, or partly cloudy 71% of the time.
The cloudier part of the year begins around May 23 and lasts for 4.9 months, ending around October 19.
The cloudiest month of the year in Key West is September, during which on average the sky is overcast or mostly cloudy 66% of the time.
Cloud Cover Categories in Key West
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Key West varies significantly throughout the year.
The wetter season lasts 4.7 months, from May 24 to October 16, with a greater than 36% chance of a given day being a wet day. The month with the most wet days in Key West is September, with an average of 17.0 days with at least 0.04 inches of precipitation.
The drier season lasts 7.3 months, from October 16 to May 24. The month with the fewest wet days in Key West is March, with an average of 4.2 days with at least 0.04 inches of precipitation.
Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone in Key West is September, with an average of 17.0 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 59% on September 16.
Daily Chance of Precipitation in Key West
To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Key West experiences extreme seasonal variation in monthly rainfall.
Rain falls throughout the year in Key West. The month with the most rain in Key West is September, with an average rainfall of 6.1 inches.
The month with the least rain in Key West is December, with an average rainfall of 1.4 inches.
Average Monthly Rainfall in Key West
The length of the day in Key West varies over the course of the year. In 2023, the shortest day is December 21, with 10 hours, 37 minutes of daylight; the longest day is June 21, with 13 hours, 40 minutes of daylight.
Hours of Daylight and Twilight in Key West
The earliest sunrise is at 6:36 AM on November 5, and the latest sunrise is 1 hour, 3 minutes later at 7:39 AM on March 12. The earliest sunset is at 5:37 PM on November 29, and the latest sunset is 2 hours, 42 minutes later at 8:20 PM on July 2.
Daylight saving time (DST) is observed in Key West during 2023, starting in the spring on March 12, lasting 7.8 months, and ending in the fall on November 5.
Sunrise & Sunset with Twilight and Daylight Saving Time in Key West
The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.
Solar Elevation and Azimuth in Key West
The figure below presents a compact representation of key lunar data for 2023. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases.
Moon Rise, Set & Phases in Key West
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.
Key West experiences extreme seasonal variation in the perceived humidity.
The muggier period of the year lasts for 8.6 months, from March 25 to December 13, during which time the comfort level is muggy, oppressive, or miserable at least 56% of the time. The month with the most muggy days in Key West is August, with 31.0 days that are muggy or worse.
The month with the fewest muggy days in Key West is February, with 12.8 days that are muggy or worse.
Humidity Comfort Levels in Key West
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
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 experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 6.9 months, from October 7 to May 4, with average wind speeds of more than 11.9 miles per hour. The windiest month of the year in Key West is November, with an average hourly wind speed of 14.4 miles per hour.
The calmer time of year lasts for 5.1 months, from May 4 to October 7. The calmest month of the year in Key West is July, with an average hourly wind speed of 9.5 miles per hour.
Average Wind Speed in Key West
The predominant average hourly wind direction in Key West is from the east throughout the year.
Wind Direction in Key West
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 water temperature experiences some seasonal variation over the course of the year.
The time of year with warmer water lasts for 3.8 months, from June 17 to October 9, with an average temperature above 83°F. The month of the year in Key West with the warmest water is August, with an average temperature of 86°F.
The time of year with cooler water lasts for 3.3 months, from December 19 to March 30, with an average temperature below 76°F. The month of the year in Key West with the coolest water is February, with an average temperature of 74°F.
Average Water Temperature in Key West
To characterize how pleasant the weather is in Key West throughout the year, we compute two travel scores.
The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Key West for general outdoor tourist activities is from mid November to mid April, with a peak score in the second week of February.
Tourism Score in Key West
The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best times of year to visit Key West for hot-weather activities are from mid March to mid May and from late October to late November, with a peak score in the last week of April.
Beach/Pool Score in Key West
For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.
Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.
Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.
Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.
Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.
Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).
Temperatures in Key West are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.
Time Spent in Various Temperature Bands and the Growing Season in Key West
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.
Growing Degree Days in Key West
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 experiences significant seasonal variation over the course of the year.
The brighter period of the year lasts for 2.0 months, from March 21 to May 22, with an average daily incident shortwave energy per square meter above 6.3 kWh. The brightest month of the year in Key West is April, with an average of 6.7 kWh.
The darker period of the year lasts for 2.5 months, from November 9 to January 25, with an average daily incident shortwave energy per square meter below 4.4 kWh. The darkest month of the year in Key West is December, with an average of 3.9 kWh.
Average Daily Incident Shortwave Solar Energy in Key West
For the purposes of this report, the geographical coordinates of Key West are 24.555 deg latitude, -81.782 deg longitude, and 3 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, 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 Algorithms 2nd Edition , 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 airports and weather stations are provided by AskGeo.com .
Maps are © OpenStreetMap contributors.
The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.
We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.
We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.
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