San Francisco weather in January
In January, San Francisco has daytime highs averaging 14 °C, nights around 6.5 °C, with 9.5 wet days, and a sea temperature of 12 °C. Figures are 1991–2020 climate normals.
- 13.9°C Average high
- 6.5°C Average low
- 9.5days Wet days
- 97mm Rainfall
- 11.6°C Sea temperature
- 9.8h Daylight
Daily temperatures through January
How January develops
Averages for the first, middle and last part of the month, from daily 1991–2020 normals. Chance of rain is the share of years in which that calendar day recorded more than 1 mm.
| Days | Avg high | Avg low | Chance of rain |
|---|---|---|---|
| 1–10 January | 13.4 °C | 6.2 °C | 32 % |
| 11–20 January | 14.0 °C | 6.5 °C | 27 % |
| 21–31 January | 14.2 °C | 6.8 °C | 33 % |
- Rain is most likely over days 21–31 of January (33 % of days) and least likely over days 11–20 (27 %).
What to expect
| Measure | Typical January | Share of the month |
|---|---|---|
| Days above 25 °C | 0 of 31 | 0 % |
| Days above 30 °C | 0 of 31 | 0 % |
| Days below 0 °C | 0.3 of 31 | 1 % |
| Days with more than 1 mm rain | 9.5 of 31 | 31 % |
Conditions in January
| Measure | Average |
|---|---|
| Mean temperature | 9.7 °C |
| Record high (1991–2020) | 21 °C |
| Record low (1991–2020) | -1.3 °C |
| Relative humidity | 83 % |
| Wind speed | 15 km/h |
| Cloud cover | 62 % |
January compared with the months around it
| Month | Avg high | Rainfall | Cloud |
|---|---|---|---|
| January | 13.9 °C | 97 mm | 62 % |
| February | 15.0 °C | 100 mm | 60 % |
| March | 16.1 °C | 75 mm | 58 % |
| November | 16.9 °C | 46 mm | 51 % |
| December | 13.8 °C | 90 mm | 58 % |
See all twelve months for San Francisco
- January is the 11th warmest month here.
- It is the 11th driest month of the year.
- It ranks 12th for least cloud cover.
- Days last about 9.8 hours from sunrise to sunset.
- It rains on 9.5 of 31 days — 31 % of the month.
- Nights are about 7.4 °C cooler than the middle of the day.
- The hottest January day on record since 1991 reached 21 °C, 7.5 °C above the usual daytime high.
- Beach score: 12 / 100 — see how this is calculated.
QuestionsJanuary in San Francisco, answered
How warm is San Francisco in January?
Daily highs average 14 °C and nights fall to about 6.5 °C, a spread of 7.4 °C between afternoon and dawn. That makes January the 12th warmest month of the year here.
Does it rain much in San Francisco in January?
January averages 97 mm of rain, spread over about 10 of the 31 days — 31 % of the month. Cloud cover averages 62 % of the sky.
Is the sea warm enough to swim in January?
The sea averages 12 °C off San Francisco in January. Most people find water below 20 °C bracing and above 25 °C comfortable for a long swim; this figure is a monthly surface average, so a sheltered bay on a still afternoon can be warmer.
How long are the days in January?
San Francisco averages 9.8 hours between sunrise and sunset in January. Day length is computed from latitude and date, so it is exact rather than modelled — but it says nothing about how much of that time is sunny.
Data sources and method
- ERA5 / ERA5-Land reanalysis — Copernicus Climate Change Service (C3S), ECMWF. Copernicus Licence
- Open-Meteo — Open-Meteo.com. CC BY 4.0
- NOAA OISST v2.1 — NOAA Physical Sciences Laboratory. Public domain
- GeoNames — GeoNames.org. CC BY 4.0
- Normal period
- 1991–2020
- Dataset version
- era5-1991-2020-scores1.1
- Last processed
Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: daylight hours, beach and comfort scores, monthly rankings, threshold day counts, chance of a wet day by date, ten-day averages within the month. Full formulas are on the methodology page.
Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.