San Francisco Weather Averages
San Francisco, California enjoys mild temperatures year round. Most days have highs in the mid 50s or 60s °F (13 to 21 °C). Extreme cold or heat are unheard of here. What does vary across the months is rainfall. The weather fluctuates from wet winters to dry summers.
This page gives detailed information on the annual temperature, precipitation, sun, humidity, wind and storm averages for San Francisco.
The temperature, rainfall, sunshine and wind speed numbers here are historical averages based on climate data gathered in downtown San Francisco near the corner of Buchanan and Hermann Streets. The rest of the measurements are averages at the San Francisco International Airport, located south of the city center.
|64 °F||annual average high||18 °C|
|51 °F||annual average low||10 °C|
San Francisco's coldest days of the year usually occur from late December to early January when the daily maximum temperature averages 56 degrees Fahrenheit (13 degrees Celsius) and the minimum averages 45 °F (7 °C).
The year's hottest days are normally in late September. The average temperature peaks then with daily highs of 70 °F (21 °C). The hottest nights occur from late August to early September with an average low of 55 °F (13 °C).
|69 days||70 °F max. or more (21 °C)|
|146 days||50 °F min. or less (10 °C)|
Every day in San Francisco normally warms to over 40 °F (4 °C), and most reach 50 °F (10 °C). The city averages just 2 days a year when the thermometer reaches into the 90s °F (over 32 °C). The temperature normally doesn't climb above 100 °F (38 °C), even on the hottest days.
The thermometer dips to 40 °F (4 °C) or below on an average of 5 nights a year. It drops to freezing here usually only once a decade.
|23.7 in||total precipitation||601 mm|
|73 days||of rain or snowfall|
December is most often the wettest month of the year in San Francisco, while July is the driest. It normally doesn't snow in San Francisco.
|160 days||clear skies|
The sun's rays reach the ground in San Francisco during 66 percent of daylight hours on average year round, for a total of 2938 hours annually. Typically on 160 days a year the sky is mainly clear, with at most 30 percent cloud cover.
Sunlight in San Francisco averages 12 hours and 11 minutes a day. The shortest days of the year in mid December have 9 hours and 33 minutes of daylight. The year's longest days in mid June last 14:47 from sunrise to sunset.
|74 %||average humidity|
The annual average for relative humidity in San Francisco ranges throughout the day from 84 percent at 4:00 am to 59 percent at 1:00 pm.
|Local Time||1 am||4 am||7 am||10 am||1 pm||4 pm||7 pm||10 pm|
|8.7 mph||wind speed average||14.0 kph|
July is usually the windiest month for San Francisco, while the wind is calmest during November.
|5 days||precipitation of 1 inch (25 mm) or more|
|3 days||with thunderstorms a year|
Almost all of the heavy rain at San Francisco falls during winter, from November to February.
Thunderstorms most commonly appear over the city during January and February, but can occur in any month except June.
These weather data are long-term historical averages provided by the National Climatic Data Center of the United States. The temperature and precipitation numbers are 1981-2010 normals while the humidity and thunderstorm statistics are 1961-1990 normals.