Average Weather in December in San Francisco Costa Rica
In San Francisco, the month of December is characterized by essentially constant daily high temperatures, with daily highs around 78°F throughout the month, rarely exceeding 81°F or dropping below 74°F.
Daily low temperatures are around 64°F, rarely falling below 61°F or exceeding 67°F. The highest daily average low temperature is 64°F on December 23.
For reference, on April 7, the hottest day of the year, temperatures in San Francisco typically range from 65°F to 82°F, while on September 21, the coldest day of the year, they range from 64°F to 78°F.
Average High and Low Temperature in December
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
The month of December in San Francisco experiences very rapidly decreasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy decreasing from 61% to 37%.
The clearest day of the month is December 31, with clear, mostly clear, or partly cloudy conditions 63% of the time.
For reference, on June 5, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 95%, while on January 2, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 64%.
Cloud Cover Categories in December
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In San Francisco, the chance of a wet day over the course of December is very rapidly decreasing, starting the month at 27% and ending it at 13%.
For reference, the year's highest daily chance of a wet day is 51% on October 7, and its lowest chance is 6% on March 16.
Probability of Precipitation in December
The average sliding 31-day rainfall during December in San Francisco is rapidly decreasing, starting the month at 3.0 inches, when it rarely exceeds 6.4 inches or falls below 0.5 inches, and ending the month at 1.4 inches, when it rarely exceeds 3.1 inches or falls below 0.1 inches.
Average Monthly Rainfall in December
Over the course of December in San Francisco, the length of the day is essentially constant. The shortest day of the month is December 20, with 11 hours, 33 minutes of daylight and the longest day is December 1, with 11 hours, 35 minutes of daylight.
Hours of Daylight and Twilight in December
The earliest sunrise of the month in San Francisco is 5:38 AM on December 1 and the latest sunrise is 15 minutes later at 5:53 AM on December 31.
The earliest sunset is 5:13 PM on December 1 and the latest sunset is 13 minutes later at 5:26 PM on December 31.
Daylight saving time is not observed in San Francisco during 2017.
For reference, on June 21, the longest day of the year, the Sun rises at 5:17 AM and sets 12 hours, 43 minutes later, at 5:59 PM, while on December 21, the shortest day of the year, it rises at 5:48 AM and sets 11 hours, 33 minutes later, at 5:21 PM.
Sunrise & Sunset with Twilight in December
The chance that a given day will be muggy in San Francisco is rapidly decreasing during December, falling from 22% to 6% over the course of the month.
For reference, on June 4, the muggiest day of the year, there are muggy conditions 60% of the time, while on January 24, the least muggy day of the year, there are muggy conditions 3% of the time.
Humidity Comfort Levels in December
The average hourly wind speed in San Francisco is gradually increasing during December, increasing from 2.9 miles per hour to 3.7 miles per hour over the course of the month.
For reference, on February 5, the windiest day of the year, the daily average wind speed is 4.0 miles per hour, while on September 18, the calmest day of the year, the daily average wind speed is 1.9 miles per hour.
Average Wind Speed in December
Wind Direction in December
San Francisco 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 Francisco is essentially constant during December, remaining around 82°F throughout.
Average Water Temperature in December
The average daily incident shortwave solar energy in San Francisco is gradually increasing during December, rising by 0.8 kWh, from 4.7 kWh to 5.5 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in December
For the purposes of this report, the geographical coordinates of San Francisco are 9.993 deg latitude, -84.129 deg longitude, and 3,583 ft elevation.
The topography within 2 miles of San Francisco contains very significant variations in elevation, with a maximum elevation change of 846 feet and an average elevation above sea level of 3,599 feet. Within 10 miles contains very significant variations in elevation (7,510 feet). Within 50 miles also contains extreme variations in elevation (11,447 feet).
The area within 2 miles of San Francisco is covered by grassland (71%) and trees (26%), within 10 miles by grassland (46%) and trees (39%), and within 50 miles by trees (54%) and grassland (17%).
This report illustrates the typical weather in San Francisco 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, Juan Santamaría International Airport, in our network suitable to be used as a proxy for the historical temperature and dew point records of San Francisco.
At a distance of 9 kilometers from San Francisco, 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 San Francisco 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.
Time zones for aiports and weather stations are provided by AskGeo.com .