January weather forecastSan Francisco, CA
January
Weather in January
The San Francisco winter persists into January, with grey skies often casting over the city. Compared to December, January receives slightly less rain but this month retains the highest average rainfall of the year at 1.02in. Fog often blankets the city, reducing visibility and creating a mystical atmosphere. Despite the relative humidity and wetness, the daily sunshine hours keep the afternoons pleasant. Leading into February, one might see a slight increase in overall temperatures.Temperature
San Francisco's weather in January, with an average high-temperature of a still refreshing 56.3°F (13.5°C), subtly shifts from December's 55.8°F (13.2°C). Throughout January, San Francisco witnesses a consistent average low-temperature of 45.9°F (7.7°C).Humidity
In January, the average relative humidity in San Francisco is 73%.Rainfall
In San Francisco, in January, during 8.2 rainfall days, 1.02" (26mm) of precipitation is typically accumulated. In San Francisco, during the entire year, the rain falls for 58.6 days and collects up to 6.46" (164mm) of precipitation.Ocean temperature
In January, the average ocean temperature is 53.2°F (11.8°C).Note: Danger awaits those who swim in 53.2°F (11.8°C) without protection. Falling below 50°F (10°C) means intense cold shock and hyperventilation.
Daylight
The average length of the day in January is 9h and 55min.On the first day of January in San Francisco, sunrise is at 7:24 am and sunset at 5:01 pm. On the last day of the month, sunrise is at 7:14 am and sunset at 5:31 pm PST.
Sunshine
The average sunshine in January in San Francisco, California, is 6.1h.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 health risk from exposure to the Sun's UV radiation for the average person.Note: In January, a daily maximum UV index of 3 leads to the following instructions:
Take necessary precautions - Defending against sun damage is advocated. The Sun is at its harshest during midday; protect yourself by staying in shaded areas and minimizing exposure. 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 January
San Francisco, CA
- Average high temperature in January: 56.3°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 January: 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 January
San Francisco, CA
- Average pressure in January: 30.13"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 January
San Francisco, CA
- Average wind speed in January: 5.8mph
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 January
San Francisco, CA
- Average humidity in January: 73%
The month with the highest relative humidity is March (76%).
The month with the lowest relative humidity is October (67%).
Average rainfall in January
San Francisco, CA
- Average rainfall in January: 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 January
San Francisco, CA
- Average rainfall days in January: 8.2 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 January
San Francisco, CA
- Average sea temperature in January: 53.2°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 January /
Average sunshine in January
San Francisco, CA
- Average daylight in January: 9h and 54min
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 January: 6h and 6min
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 January
San Francisco, CA
- Average sunshine days in January: 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 January
San Francisco, CA
- Average UV index in January: 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 January
San Francisco, CA
- Average cloud cover in January: 33
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 January
San Francisco, CA
- Average visibility in January: 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).
