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Average Weather in December in San Diego California, United States

In San Diego, the month of December is characterized by gradually falling daily high temperatures, with daily highs decreasing by 2°F, from 67°F to 65°F over the course of the month, and rarely exceeding 74°F or dropping below 59°F. The lowest daily average high temperature is 65°F on December 26.

Daily low temperatures decrease by 2°F, from 52°F to 50°F, rarely falling below 44°F or exceeding 58°F. The lowest daily average low temperature is 50°F on December 28.

For reference, on August 26, the hottest day of the year, temperatures in San Diego typically range from 68°F to 77°F, while on December 28, the coldest day of the year, they range from 50°F to 65°F.

Average High and Low Temperature in December

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

Average Hourly Temperature in December in San Diego18152229112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313112 AM4 AM8 AM12 PM4 PM8 PM12 AMNovJancomfortablecoldcool
The average hourly temperature, color coded into bands: frigid < 15°F < freezing < 32°F < chilly < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The shaded overlays indicate night and civil twilight.

Clouds

The month of December in San Diego 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 highest chance of overcast or mostly cloudy conditions is 38% on December 28.

The clearest day of the month is December 1, with clear, mostly clear, or partly cloudy conditions 65% of the time.

For reference, on February 20, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 43%, while on September 10, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 91%.

Cloud Cover Categories in December

Cloud Cover Categories in December in San Diego1815222911223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%NovJanSep 1091%Sep 1091%Dec 165%Dec 165%Dec 3162%Dec 3162%Dec 1165%Dec 1165%Dec 2162%Dec 2162%clearmostly clearpartly cloudymostly cloudyovercast
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.

Precipitation

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In San Diego, the chance of a wet day over the course of December is increasing, starting the month at 12% and ending it at 17%.

For reference, the year's highest daily chance of a wet day is 20% on February 22, and its lowest chance is 0% on June 27.

Probability of Precipitation in December

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 San Diego is increasing, starting the month at 1.2 inches, when it rarely exceeds 2.8 inches, and ending the month at 1.9 inches, when it rarely exceeds 4.9 inches or falls below 0.1 inches.

Average Monthly Rainfall in December

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 liquid-equivalent snowfall.

Sun

Over the course of December in San Diego, the length of the day is essentially constant. The shortest day of the month is December 21, with 9 hours, 60 minutes of daylight and the longest day is December 1, with 10 hours, 9 minutes of daylight.

Hours of Daylight and Twilight in December

Hours of Daylight and Twilight in December in San Diego1815222911223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hrNovJanDec 219 hr, 60 minDec 219 hr, 60 minnightnightdaydayDec 110 hr, 9 minDec 110 hr, 9 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 San Diego is 6:33 AM on December 1 and the latest sunrise is 18 minutes later at 6:50 AM on December 31.

The earliest sunset is 4:42 PM on December 3 and the latest sunset is 11 minutes later at 4:53 PM on December 31.

Daylight saving time is observed in San Diego during 2017, 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 5:41 AM and sets 14 hours, 18 minutes later, at 7:59 PM, while on December 21, the shortest day of the year, it rises at 6:47 AM and sets 9 hours, 60 minutes later, at 4:46 PM.

Sunrise & Sunset with Twilight and Daylight Saving Time in December

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.

Humidity

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 San Diego is essentially constant during December, remaining around 0% throughout.

For reference, on August 27, the muggiest day of the year, there are muggy conditions 23% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 0% of the time.

Humidity Comfort Levels in December

The percentage of time spent at various humidity comfort levels, categorized by dew point: dry < 55°F < comfortable < 60°F < humid < 65°F < muggy < 70°F < oppressive < 75°F < miserable.

Wind

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 San Diego is essentially constant during December, remaining within 0.1 miles per hour of 4.2 miles per hour throughout.

For reference, on December 11, the windiest day of the year, the daily average wind speed is 4.3 miles per hour, while on August 23, the calmest day of the year, the daily average wind speed is 3.2 miles per hour.

The highest daily average wind speed during December is 4.3 miles per hour on December 11.

Average Wind Speed in December

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 San Diego throughout December is predominantly from the east, with a peak proportion of 40% on December 31.

Wind Direction in December

Wind Direction in December in San DiegoWEW1815222911223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%NovJaneastwestnorthsouth
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Water Temperature

San Diego 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 San Diego is gradually decreasing during December, falling by 2°F, from 62°F to 60°F, over the course of the month.

Average Water Temperature in December

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

Solar Energy

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 San Diego is essentially constant during December, remaining within 0.1 kWh of 3.3 kWh throughout.

The lowest average daily incident shortwave solar energy during December is 3.1 kWh on December 26.

Average Daily Incident Shortwave Solar Energy in December

Average Daily Incident Shortwave Solar Energy in December in San Diego1815222911223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310.0 kWh0.5 kWh1.0 kWh1.5 kWh2.0 kWh2.5 kWh3.0 kWh3.5 kWh4.0 kWh4.5 kWh5.0 kWhNovJanDec 263.1 kWhDec 263.1 kWhDec 13.4 kWhDec 13.4 kWhDec 113.2 kWhDec 113.2 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.

Topography

For the purposes of this report, the geographical coordinates of San Diego are 32.715 deg latitude, -117.157 deg longitude, and 33 ft elevation.

The topography within 2 miles of San Diego contains only modest variations in elevation, with a maximum elevation change of 305 feet and an average elevation above sea level of 93 feet. Within 10 miles contains only modest variations in elevation (1,552 feet). Within 50 miles contains very significant variations in elevation (6,483 feet).

The area within 2 miles of San Diego is covered by artificial surfaces (72%) and water (21%), within 10 miles by artificial surfaces (56%) and water (37%), and within 50 miles by water (48%) and shrubs (33%).

Data Sources

This report illustrates the typical weather in San Diego 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 are 3 weather stations near enough to contribute to our estimation of the temperature and dew point in San Diego.

For each station, the records are corrected for the elevation difference between that station and San Diego according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.

The estimated value at San Diego is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between San Diego and a given station.

The stations contributing to this reconstruction are: San Diego International Airport (58%, 3.2 kilometers, northwest); Naval Air Station North Island (37%, 4.4 kilometers, southwest); and Ream Field (4.9%, 17 kilometers, south).

Other Data

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.