December weather forecastSan Francisco, CA
December weather for San Francisco, California: December is the month when San Francisco, California, sees the lowest average temperatures, with a high of 55.8°F (13.2°C) and a low of 45.9°F (7.7°C). The month with the least sunshine in San Francisco, California, is December, with an average of 5.8h of sunshine.
December
Weather in December
With the arrival of December, San Francisco plunges into winter. Lower temperatures from November's relatively mild condition characterize this month. Despite the winter season, San Francisco's winter is typically milder than much of the United States, with temperatures rarely dropping to freezing point. The city's holiday season's festivities are in full swing, imbued with a spirit of celebration and cheer. The transition to a new year yields January's promise of slightly cooler temperatures, marking full-circle the city's unique, appealing climate.Temperature
December is the month when San Francisco, California, sees the lowest average temperatures, with a high of 55.8°F (13.2°C) and a low of 45.9°F (7.7°C).Humidity
In December, the average relative humidity in San Francisco, California, is 72%.Rainfall
In December, the rain falls for 8.4 days. Throughout December, 1.02" (26mm) of precipitation is accumulated. Throughout the year, in San Francisco, there are 58.6 rainfall days, and 6.46" (164mm) of precipitation is accumulated.Ocean temperature
In December, the average ocean temperature is 54.5°F (12.5°C).Note: In 54.5°F (12.5°C), even brief exposure to 55.4°F (13°C) feels biting, and anything less than 50°F (10°C) risks cold shock and impaired breathing, considering one's health.
Daylight
December has the shortest days of the year in San Francisco, with an average of 9h and 36min of daylight.On the first day of the month, sunrise is at 7:06 am and sunset at 4:51 pm. On the last day of December, in San Francisco, sunrise is at 7:24 am and sunset at 5:01 pm PST.
Sunshine
The month with the least sunshine is December, with an average of 5.8h of sunshine.UV index
The months with the lowest UV index are January, February, November and December, with an average maximum UV index of 3. A UV Index value of 3 to 5 symbolizes a moderate threat to health from unprotected exposure to Sun's UV rays for average individuals.Note: The UV index of 3 during December leads to these advisories:
Take measures. Individuals with light skin might experience burns in under 30 minutes. Sun's radiation is most powerful around mid-day, so it's best to limit outdoor activities during this time. Sunglasses providing both UVA and UVB protection are non-negotiable on sunlit days.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
San Francisco, CA
- Average high temperature in December: 55.8°F
The warmest month (with the highest average high temperature) is September (73.2°F).
The month with the lowest average high temperature is December (55.8°F).
- Average low temperature in December: 45.9°F
The month with the highest average low temperature is September (56.7°F).
The coldest months (with the lowest average low temperature) are January and December (45.9°F).
Average pressure in December
San Francisco, CA
- Average pressure in December: 30.11"Hg
The month with the highest atmospheric pressure is January (30.13"Hg).
The months with the lowest atmospheric pressure are June, August and September (29.92"Hg).
Average wind speed in December
San Francisco, CA
- Average wind speed in December: 6.3mph
The windiest month (with the highest average wind speed) is May (7.6mph).
The calmest month (with the lowest average wind speed) is November (5.5mph).
Average humidity in December
San Francisco, CA
- Average humidity in December: 72%
The month with the highest relative humidity is March (76%).
The month with the lowest relative humidity is October (67%).
Average rainfall in December
San Francisco, CA
- Average rainfall in December: 1.02"
The wettest month (with the highest rainfall) is February (1.38").
The driest months (with the least rainfall) are July, August and September (0.08").
Average rainfall days in December
San Francisco, CA
- Average rainfall days in December: 8.4 days
The month with the highest number of rainy days is March (9.3 days).
The month with the least rainy days is June (1.9 days).
Average sea temperature in December
San Francisco, CA
- Average sea temperature in December: 54.5°F
The best month for swimming (with the highest average sea temperature) is September (57.3°F).
The coldest months (with the lowest average sea temperature) are April and June (53°F).
Average daylight in December /
Average sunshine in December
San Francisco, CA
- Average daylight in December: 9h and 36min
The month with the longest days is June (Average daylight: 14h and 42min).
The month with the shortest days is December (Average daylight: 9h and 36min).
- Average sunshine in December: 5h and 48min
The month with the most sunshine is July (Average sunshine: 11h and 48min).
The month with the least sunshine is December (Average sunshine: 5h and 48min).
Average sunshine days in December
San Francisco, CA
- Average sunshine days in December: 22 days
The month with the most sunshine days is October (25.8 days).
The month with the least sunshine days is March (20.8 days).
Average UV index in December
San Francisco, CA
- Average UV index in December: 3
The months with the highest UV index are April, June, July, August and September (UV index 5).
The months with the lowest UV index are January, February, November and December (UV index 3).
Average cloud cover in December
San Francisco, CA
- Average cloud cover in December: 35
The month with the most cloud cover is March (Cloud cover 36).
The months with the least cloud cover are July and September (Cloud cover 14).
Average visibility in December
San Francisco, CA
- Average visibility in December: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
