Average Weather in August in San Francisco California, United States
Daily high temperatures are around 70°F, rarely falling below 64°F or exceeding 79°F.
Daily low temperatures are around 57°F, rarely falling below 54°F or exceeding 62°F.
For reference, on September 19, the hottest day of the year, temperatures in San Francisco typically range from 58°F to 72°F, while on January 3, the coldest day of the year, they range from 45°F to 56°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
La Serena, Chile (5,732 miles away); Cilaos, Réunion (11,292 miles); and Albany, Australia (9,147 miles) are the far-away foreign places with temperatures most similar to San Francisco (view comparison).
The month of August in San Francisco experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 9% throughout the month.
The clearest day of the month is August 7, with clear, mostly clear, or partly cloudy conditions 92% of the time.
For reference, on January 11, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 55%, while on July 19, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 92%.
Cloud Cover Categories in August
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
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 essentially constant, remaining about 0.0 inches throughout, and rarely exceeding 0.2 inches.
Average Monthly Rainfall in August
Over the course of August in San Francisco, the length of the day is rapidly decreasing. From the start to the end of the month, the length of the day decreases by 1 hour, 4 minutes, implying an average daily decrease of 2 minutes, 8 seconds, and weekly decrease of 14 minutes, 55 seconds.
The shortest day of the month is August 31, with 13 hours, 0 minutes of daylight and the longest day is August 1, with 14 hours, 4 minutes of daylight.
Hours of Daylight and Twilight in August
The earliest sunrise of the month in San Francisco is 6:13 AM on August 1 and the latest sunrise is 26 minutes later at 6:39 AM on August 31.
The latest sunset is 8:17 PM on August 1 and the earliest sunset is 38 minutes earlier at 7:39 PM on August 31.
Daylight saving time is observed in San Francisco during 2020, but it neither starts nor ends during August, so the entire month is in daylight saving time.
For reference, on June 20, the longest day of the year, the Sun rises at 5:47 AM and sets 14 hours, 47 minutes later, at 8:34 PM, while on December 21, the shortest day of the year, it rises at 7:21 AM and sets 9 hours, 33 minutes later, at 4:54 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 essentially constant during August, remaining around 0% throughout.
For reference, on August 21, the muggiest day of the year, there are muggy conditions 0% 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 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 0.2 miles per hour of 8.1 miles per hour throughout.
For reference, on May 29, the windiest day of the year, the daily average wind speed is 9.7 miles per hour, while on October 20, the calmest day of the year, the daily average wind speed is 7.2 miles per hour.
Average Wind Speed in August
The hourly average wind direction in San Francisco throughout August is predominantly from the west, with a peak proportion of 93% on August 9.
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 around 57°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 increasing during August, increasing by 370°F, from 1,592°F to 1,962°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 decreasing during August, falling by 1.1 kWh, from 7.9 kWh to 6.8 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in August
For the purposes of this report, the geographical coordinates of San Francisco are 37.775 deg latitude, -122.419 deg longitude, and 59 ft elevation.
The topography within 2 miles of San Francisco contains significant variations in elevation, with a maximum elevation change of 597 feet and an average elevation above sea level of 128 feet. Within 10 miles contains significant variations in elevation (1,270 feet). Within 50 miles contains very significant variations in elevation (3,894 feet).
The area within 2 miles of San Francisco is covered by artificial surfaces (82%) and water (15%), within 10 miles by water (62%) and artificial surfaces (29%), and within 50 miles by water (41%) and grassland (20%).
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 are 2 weather stations near enough to contribute to our estimation of the temperature and dew point in San Francisco.
For each station, the records are corrected for the elevation difference between that 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.
The estimated value at San Francisco is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between San Francisco and a given station.
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 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.