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December Weather in Key West Florida, United States

Daily high temperatures decrease by 3°F, from 78°F to 75°F, rarely falling below 67°F or exceeding 82°F.

Daily low temperatures decrease by 4°F, from 70°F to 67°F, rarely falling below 56°F or exceeding 76°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 December in Key West

The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on December. 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 December in Key West

Average Hourly Temperature in December in Key WestDec112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313112 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMNovJancomfortablewarm
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
The average hourly temperature, color coded into bands. The shaded overlays indicate night and civil twilight.

Hengchun, Taiwan (8,892 miles away) is the far-away foreign place with temperatures most similar to Key West (view comparison).

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The month of December in Key West experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 36% throughout the month.

The clearest day of the month is December 2, 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 Categories in December in Key West

Cloud Cover Categories in December in Key WestDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%NovJanDec 165%Dec 165%Dec 3163%Dec 3163%Dec 1164%Dec 1164%Dec 2164%Dec 2164%clearmostly clearpartly cloudymostly cloudyovercast
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds.

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 December is essentially constant, remaining around 14% throughout.

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 December in Key West

The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

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 December in Key West is essentially constant, remaining about 1.5 inches throughout, and rarely exceeding 4.3 inches or falling below 0.1 inches.

The lowest average 31-day accumulation is 1.4 inches on December 26.

Average Monthly Rainfall in December in Key West

The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average snowfall.

Over the course of December in Key West, the length of the day is essentially constant. The shortest day of the month is December 22, with 10 hours, 37 minutes of daylight and the longest day is December 1, with 10 hours, 44 minutes of daylight.

Hours of Daylight and Twilight in December in Key West

Hours of Daylight and Twilight in December in Key WestDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hrNovJanDec 2110 hr, 37 minDec 2110 hr, 37 minnightnightdaydayDec 110 hr, 44 minDec 110 hr, 44 min
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise of the month in Key West is 6:54 AM on December 1 and the latest sunrise is 17 minutes later at 7:10 AM on December 31.

The earliest sunset is 5:37 PM on December 1 and the latest sunset is 11 minutes later at 5:49 PM on December 31.

Daylight saving time is observed in Key West during 2023, but it neither starts nor ends during December, so the entire month is in standard 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 22, the shortest day of the year, it rises at 7:07 AM and sets 10 hours, 37 minutes later, at 5:44 PM.

Sunrise & Sunset with Twilight and Daylight Saving Time in December in Key West

Sunrise & Sunset with Twilight and Daylight Saving Time in December in Key WestDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031312 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMNovJan6:54 AM6:54 AMDec 15:37 PMDec 15:37 PM7:10 AM7:10 AMDec 315:49 PMDec 315:49 PM7:03 AM7:03 AMDec 165:41 PMDec 165:41 PMSolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day over the course of December. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

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 December in Key West

Solar Elevation and Azimuth in December in Key WestDec112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313112 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMNovJan001010202030304040001010202030304040
northeastsouthwest
Solar elevation and azimuth over the course of December 2023. The black lines are lines of constant solar elevation (the angle of the sun above the horizon, in degrees). The background color fills indicate the azimuth (the compass bearing) of the sun. The lightly tinted areas at the boundaries of the cardinal compass points indicate the implied intermediate directions (northeast, southeast, southwest, and northwest).

The figure below presents a compact representation of key lunar data for December 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. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

Moon Rise, Set & Phases in December in Key West

Moon Rise, Set & Phases in December in Key WestDec112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313112 AM12 AM4 AM4 AM8 AM8 AM12 PM12 PM4 PM4 PM8 PM8 PM12 AM12 AMNovJanNov 134:28 AMNov 134:28 AMNov 274:17 AMNov 274:17 AMDec 126:33 PMDec 126:33 PMDec 267:34 PMDec 267:34 PMJan 116:58 AMJan 116:58 AMJan 2512:55 PMJan 2512:55 PM6:53 AM6:53 AM5:52 PM5:52 PM5:03 PM5:03 PM7:07 AM7:07 AM6:43 AM6:43 AM5:22 PM5:22 PM5:27 PM5:27 PM7:51 AM7:51 AM7:32 AM7:32 AM6:16 PM6:16 PM6:10 PM6:10 PM8:00 AM8:00 AM
The time in which the moon is above the horizon (light blue area), with new moons (dark gray lines) and full moons (blue lines) indicated. The shaded overlays indicate night and civil twilight.
Dec 2023IlluminationMoonriseMoonsetMoonriseMeridian PassingDistance
1
84%-10:48 AMWNW9:34 PMENE3:44 AMN246,913 mi
2
76%-11:29 AMWNW10:29 PMENE4:34 AMS249,041 mi
3
67%-12:05 PMWNW11:23 PMENE5:19 AMS250,517 mi
4
58%-12:37 PMWNW-6:02 AMS251,208 mi
5
50%12:14 AME1:06 PMW-6:42 AMS251,043 mi
6
38%1:04 AME1:35 PMW-7:21 AMS250,024 mi
7
29%1:55 AME2:04 PMW-8:00 AMS248,216 mi
8
20%2:46 AME2:34 PMW-8:41 AMS245,757 mi
9
13%3:41 AMESE3:08 PMWSW-9:24 AMS242,837 mi
10
6%4:38 AMESE3:46 PMWSW-10:11 AMS239,692 mi
11
2%5:39 AMESE4:30 PMWSW-11:04 AMS236,582 mi
12
0%6:43 AMESE5:22 PMWSW-12:02 PMS233,763 mi
13
1%7:48 AMESE6:21 PMWSW-1:05 PMS231,453 mi
14
4%8:50 AMESE7:27 PMWSW-2:09 PMS229,801 mi
15
10%9:46 AMESE8:35 PMWSW-3:11 PMS228,864 mi
16
19%10:36 AMESE9:42 PMWSW-4:09 PMS228,606 mi
17
29%11:19 AMESE10:47 PMWSW-5:03 PMS228,930 mi
18
41%11:57 AME11:50 PMW-5:53 PMS229,711 mi
19
50%12:33 PME--6:40 PMS230,831 mi
20
64%-12:50 AMW1:07 PME7:27 PMS232,198 mi
21
75%-1:50 AMW1:41 PME8:14 PMS233,757 mi
22
84%-2:50 AMWNW2:18 PMENE9:02 PMS235,488 mi
23
91%-3:52 AMWNW2:58 PMENE9:53 PMS237,385 mi
24
96%-4:54 AMWNW3:43 PMENE10:47 PMN239,444 mi
25
99%-5:56 AMWNW4:32 PMENE11:43 PMN241,635 mi
26
100%-6:56 AMWNW5:27 PMENE--
27
100%-7:51 AMWNW6:24 PMENE12:40 AMN243,893 mi
28
98%-8:41 AMWNW7:22 PMENE1:34 AMN246,110 mi
29
95%-9:24 AMWNW8:19 PMENE2:25 AMS248,146 mi
30
90%-10:02 AMWNW9:13 PMENE3:13 AMS249,840 mi
31
83%-10:35 AMWNW10:05 PMENE3:56 AMS251,032 mi

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 rapidly decreasing during December, falling from 63% to 48% 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 least muggy day of the year, there are muggy conditions 42% of the time.

Humidity Comfort Levels in December in Key West

Humidity Comfort Levels in December in Key WestDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%NovJanDec 163%Dec 163%Dec 3148%Dec 3148%Dec 1157%Dec 1157%Dec 2153%Dec 2153%miserablemiserableoppressiveoppressivemuggymuggyhumidhumidcomfortablecomfortabledrydry
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The percentage of time spent at various humidity comfort levels, categorized by dew point.

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 essentially constant during December, remaining within 0.1 miles per hour of 14.0 miles per hour throughout.

For reference, on November 7, the windiest day of the year, the daily average wind speed is 14.6 miles per hour, while on July 29, the calmest day of the year, the daily average wind speed is 9.3 miles per hour.

Average Wind Speed in December in Key West

The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The hourly average wind direction in Key West throughout December is predominantly from the east, with a peak proportion of 56% on December 2.

Wind Direction in December in Key West

Wind Direction in December in Key WestDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%100%20%80%40%60%60%40%80%20%100%0%NovJaneastnorthsouthwest
northeastsouthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions, excluding hours in which the mean wind speed is less than 1.0 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

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 decreasing during December, falling by 2°F, from 77°F to 75°F, over the course of the month.

Average Water Temperature in December in Key West

The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

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 December in Key West

Time Spent in Various Temperature Bands and the Growing Season in December in Key WestDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%NovJan100%Dec 16100%Dec 16coolcomfortablewarmcold
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
The percentage of time spent in various temperature bands. The black line is the percentage chance that a given day is within the growing season.

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.

The average accumulated growing degree days in Key West are rapidly increasing during December, increasing by 655°F, from 9,454°F to 10,109°F, over the course of the month.

Growing Degree Days in December in Key West

Growing Degree Days in December in Key WestDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031319,200°F9,200°F9,400°F9,400°F9,600°F9,600°F9,800°F9,800°F10,000°F10,000°F10,200°F10,200°F10,400°F10,400°FNovJanDec 19,454°FDec 19,454°FDec 3110,109°FDec 3110,109°FDec 119,684°FDec 119,684°F
The average growing degree days accumulated over the course of December, with 25th to 75th and 10th to 90th percentile bands.

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 essentially constant during December, remaining within 0.1 kWh of 3.9 kWh throughout.

The lowest average daily incident shortwave solar energy during December is 3.8 kWh on December 23.

Average Daily Incident Shortwave Solar Energy in December in Key West

Average Daily Incident Shortwave Solar Energy in December in Key WestDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310.0 kWh0.0 kWh0.5 kWh0.5 kWh1.0 kWh1.0 kWh1.5 kWh1.5 kWh2.0 kWh2.0 kWh2.5 kWh2.5 kWh3.0 kWh3.0 kWh3.5 kWh3.5 kWh4.0 kWh4.0 kWh4.5 kWh4.5 kWh5.0 kWh5.0 kWh5.5 kWh5.5 kWh6.0 kWh6.0 kWhNovJanDec 233.8 kWhDec 233.8 kWhDec 14.0 kWhDec 14.0 kWh
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

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.

Other Data

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.

Disclaimer

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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