San Francisco climate

Name: San Francisco
Address: US

San Francisco is warmest in September, with average highs of 23 °C, and coldest in January, when nights average 6.5 °C. February is the wettest month (100 mm) and July the driest (0.5 mm). Figures are 1991–2020 climate normals.

Across a full year San Francisco averages 490 mm of rain, 26 days above 25 °C and 1 days below freezing.

United States · 16 m elevation · population 827,526 · 1991–2020 normals

Temperature below 0 °C to above 30 °C Rain band height is that month’s share of the wettest month

Warmest month September 23 °C
Coldest month January 6.5 °C
Driest month July 0 mm
Wettest month February 100 mm
Least cloud September 33 % cloud
Hottest on record September 39 °C
Coldest on record December -2.3 °C
Warmest sea September 14 °C

What to expectSan Francisco through the year

San Francisco has a clear annual cycle: average daily highs run from 14 °C in January to 23 °C in September, a swing of 7.3 °C in mean temperature across the year.

Counted across a normal year, 26 days a year reach 25 °C, 4 of them reach 30 °C, 1 nights drop below freezing. The warmest reading in the 1991–2020 record is 39 °C, in September.

Rain is strongly seasonal. February averages 100 mm against 0 mm in July — 215 times as much. Planning around the dry months matters more here than planning around temperature.

The sea off San Francisco is warmest in September at 14 °C and coldest in April at 12 °C. Sea temperature lags the air by a month or two, which is why late summer swims warmer than early summer at the same air temperature.

Month by month

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 %
April	17.3 °C	37 mm	48 %
May	18.9 °C	18 mm	45 %
June	21.0 °C	3 mm	35 %
July	21.4 °C	under 1 mm	38 %
August	21.9 °C	1 mm	39 %
September	22.7 °C	2 mm	33 %
October	21.2 °C	21 mm	38 %
November	16.9 °C	46 mm	51 %
December	13.8 °C	90 mm	58 %

Temperature month by month

Month	Avg high	Avg low	Mean	Record high	Record low	Days above 25 °C	Days above 30 °C
January	13.9 °C	6.5 °C	9.7 °C	21.4 °C	-1.3 °C	0	0
February	15.0 °C	7.4 °C	10.6 °C	23.1 °C	0.5 °C	0	0
March	16.1 °C	8.5 °C	11.7 °C	25.2 °C	1.4 °C	0	0
April	17.3 °C	9.2 °C	12.6 °C	30.0 °C	3.1 °C	1	0
May	18.9 °C	10.7 °C	14.2 °C	34.6 °C	6.2 °C	2	0
June	21.0 °C	11.9 °C	15.8 °C	35.1 °C	7.9 °C	4	1
July	21.4 °C	12.8 °C	16.3 °C	32.9 °C	9.6 °C	3	0
August	21.9 °C	13.4 °C	16.7 °C	33.0 °C	10.3 °C	4	0
September	22.7 °C	13.2 °C	16.9 °C	38.5 °C	9.3 °C	7	1
October	21.2 °C	12.0 °C	15.7 °C	33.8 °C	6.7 °C	5	1
November	16.9 °C	9.1 °C	12.4 °C	27.0 °C	1.1 °C	0	0
December	13.8 °C	6.8 °C	9.9 °C	20.5 °C	-2.3 °C	0	0

Rain, sun and wind month by month

Month	Rainfall	Wet days	Daylight	Cloud cover	Humidity	Wind	Sea temp
January	97 mm	10	9.8 h/day	62 %	83 %	15 km/h	11.6 °C
February	100 mm	9	11 h/day	60 %	81 %	17 km/h	11.9 °C
March	75 mm	9	12 h/day	58 %	80 %	18 km/h	12.0 °C
April	37 mm	5	13 h/day	48 %	76 %	21 km/h	11.5 °C
May	18 mm	3	14 h/day	45 %	74 %	21 km/h	11.7 °C
June	3 mm	1	15 h/day	35 %	73 %	21 km/h	12.1 °C
July	under 1 mm	0	15 h/day	38 %	77 %	20 km/h	13.4 °C
August	1 mm	0	14 h/day	39 %	77 %	19 km/h	14.2 °C
September	2 mm	0	12 h/day	33 %	75 %	18 km/h	14.4 °C
October	21 mm	3	11 h/day	38 %	74 %	16 km/h	13.7 °C
November	46 mm	6	10 h/day	51 %	78 %	15 km/h	12.9 °C
December	90 mm	9	9.6 h/day	58 %	80 %	16 km/h	12.0 °C

Where San Francisco ranks

Ranking	Position	Value
The driest places in North America in September	2nd of 50	1.7 mm
Places with the best weather in North America in September	3rd of 50	94/100
Places with the best weather in North America in August	8th of 50	93/100
The driest places in North America in July	8th of 50	0.5 mm
Places with the best weather in North America in July	11th of 50	92/100
The coolest places in North America in July	15th of 50	21 °C

Planning a trip? See the best time to visit San Francisco.

QuestionsCommon questions about San Francisco’s climate

When is the best time to visit San Francisco?

That depends on what you want, so the honest answer is a comparison rather than a single month. July, August, September sit closest to 20 °C on average, September is the warmest month and July the driest. The month-by-month table above has the full picture.

How hot does San Francisco get?

In September, the warmest month, daily highs average 23 °C. About 4 days a year pass 30 °C. The highest value in the 1991–2020 record is 39 °C.

How cold does it get in winter?

Nights average 6.5 °C in January, the coldest month. A normal year has 1 nights below freezing.

Which month is wettest in San Francisco?

February, averaging 100 mm over 9 days with rain. The driest month is July with 0 mm. The year as a whole averages 490 mm.

Are these figures a forecast?

No. They are 1991–2020 climate normals: the average of thirty years, which describes what a month is usually like in San Francisco rather than what any particular week will bring. Individual years can differ substantially from the normal.

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
Data point: 37.775°, -122.419° , 16 m above sea level (the coordinates the reanalysis values are taken for)
Dataset version: era5-1991-2020-scores1.1
Last processed: 1 August 2026

Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: monthly rankings, daylight hours, beach and comfort scores. 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.