Average Weather in August in San Francisco Mexico
Daily high temperatures are around 86°F, rarely falling below 82°F or exceeding 91°F. The highest daily average high temperature is 87°F on August 8.
Daily low temperatures are around 71°F, rarely falling below 67°F or exceeding 74°F.
For reference, on May 11, the hottest day of the year, temperatures in San Francisco typically range from 71°F to 92°F, while on January 6, the coldest day of the year, they range from 58°F to 78°F.
Average High and Low Temperature in August
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on August. 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 August
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 month of August in San Francisco experiences gradually increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 72% to 77%. The lowest chance of overcast or mostly cloudy conditions is 72% on August 2.
The clearest day of the month is August 2, with clear, mostly clear, or partly cloudy conditions 28% of the time.
For reference, on September 15, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 79%, while on March 17, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 66%.
Cloud Cover Categories in August
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. In San Francisco, the chance of a wet day over the course of August is rapidly increasing, starting the month at 67% and ending it at 74%.
For reference, the year's highest daily chance of a wet day is 74% on September 2, and its lowest chance is 14% on January 17.
Probability of Precipitation in August
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 August in San Francisco is rapidly increasing, starting the month at 6.6 inches, when it rarely exceeds 11.8 inches or falls below 2.9 inches, and ending the month at 8.6 inches, when it rarely exceeds 13.8 inches or falls below 4.5 inches.
The lowest average 31-day accumulation is 6.6 inches on August 3.
Average Monthly Rainfall in August
Over the course of August in San Francisco, the length of the day is decreasing. From the start to the end of the month, the length of the day decreases by 30 minutes, implying an average daily decrease of 1 minute, 1 second, and weekly decrease of 7 minutes, 7 seconds.
The shortest day of the month is August 31, with 12 hours, 33 minutes of daylight and the longest day is August 1, with 13 hours, 3 minutes of daylight.
Hours of Daylight and Twilight in August
The earliest sunrise of the month in San Francisco is 7:06 AM on August 1 and the latest sunrise is 9 minutes later at 7:15 AM on August 31.
The latest sunset is 8:09 PM on August 1 and the earliest sunset is 21 minutes earlier at 7:48 PM on August 31.
Daylight saving time is observed in San Francisco during 2018, but it neither starts nor ends during August, so the entire month is in daylight saving time.
For reference, on June 21, the longest day of the year, the Sun rises at 6:52 AM and sets 13 hours, 23 minutes later, at 8:15 PM, while on December 21, the shortest day of the year, it rises at 7:03 AM and sets 10 hours, 53 minutes later, at 5:56 PM.
Sunrise & Sunset with Twilight in August
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 Francisco is increasing during August, rising from 69% to 76% over the course of the month.
For reference, on September 2, the muggiest day of the year, there are muggy conditions 77% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 1% of the time.
Humidity Comfort Levels in August
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 San Francisco is essentially constant during August, remaining within 0.1 miles per hour of 5.5 miles per hour throughout.
For reference, on April 19, the windiest day of the year, the daily average wind speed is 6.7 miles per hour, while on December 17, the calmest day of the year, the daily average wind speed is 5.0 miles per hour.
The lowest daily average wind speed during August is 5.5 miles per hour on August 24.
Average Wind Speed in August
Wind Direction in August
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 August, remaining within 1°F of 84°F throughout.
Average Water Temperature in August
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 San Francisco 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 August
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.
The average accumulated growing degree days in San Francisco are rapidly increasing during August, increasing by 839°F, from 5,274°F to 6,113°F, over the course of the month.
Growing Degree Days in August
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 Francisco is essentially constant during August, remaining within 0.2 kWh of 6.0 kWh throughout.
Average Daily Incident Shortwave Solar Energy in August
For the purposes of this report, the geographical coordinates of San Francisco are 20.553 deg latitude, -98.002 deg longitude, and 1,526 ft elevation.
The topography within 2 miles of San Francisco contains very significant variations in elevation, with a maximum elevation change of 1,486 feet and an average elevation above sea level of 1,662 feet. Within 10 miles contains very significant variations in elevation (4,892 feet). Within 50 miles also contains extreme variations in elevation (10,499 feet).
The area within 2 miles of San Francisco is covered by cropland (100%), within 10 miles by cropland (89%) and trees (11%), and within 50 miles by cropland (71%) and trees (19%).
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, Tulancingo, 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 65 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.
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.
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.