San Francisco, California Climate Records and Averages

San Francisco, California enjoys a marine–type climate characterized by mild and moderately wet winters and dry, cool summers. Winter rains, occurring from November through March, account for over 80 percent of the annual rainfall and measurable precipitation occurs on an average of 10 days per month during this period. However, there are frequent dry periods lasting well over a week. Severe winter storms with gale winds and heavy rains occur only occasionally. Thunderstorms average two a year and could occur in any month.

The daily and annual range in temperature is small. A few frosty mornings occur during the winter, but the temperature seldom drops below freezing. Winter temperatures generally rise to the high 50s in the early afternoon.

The summer weather is dominated by a cool sea breeze resulting in an average summer wind speed of nearly 15 mph. Winds are light in the early morning but normally reach 20 to 25 mph in the afternoon.

A sea fog, arriving over the city during the late evening or night as a low cloud, is another persistent feature of summer weather. This fog, occasionally producing drizzle or mist, usually disappears during late morning. Despite the morning overcast, summer days are sunny. On the average a total of only 14 days during the four months from June through September are classified as cloudy.

Daytime temperatures are held down both by the morning low overcast and the afternoon strengthening sea breeze, resulting in daily maximum readings averaging about 70 degrees from May through August. September, when the sea breeze becomes less pronounced, is the warmest month with highs in the 70s. Low temperatures during the summer are in the mid–50s.

Temperature + Precipitation

  Monthly Averages Daily Extremes Monthly Extremes Max. Temp. Min. Temp.
Temperatures
 in F
Max. Min. Avg High Date of 
daily extreme
 high
Low Date of
daily extreme
low
Highest
Avg
Year Lowest
Avg
Year # Days >=
90 F
# Days <=
32 F
# Days <=
32 F
# Days<=
0 F
January 55.8 42.5 49.1 72 13/2009 26 05/1949 53.8 2003 42.4 1949 0.0 0.0 1.0 0.0
February 59.1 45.0 52.1 77 26/1986 30 14/1949 56.3 1986 46.9 1949 0.0 0.0 0.2 0.0
March 61.2 46.2 53.7 85 25/1952 31 03/1966 59.4 2004 49.7 1954 0.0 0.0 0.0 0.0
April 63.8 47.7 55.8 92 29/1981 36 27/1955 60.7 1989 50.5 1975 0.1 0.0 0.0 0.0
May 66.8 50.3 58.5 97 27/1984 39 03/1950 64.4 1997 55.2 1965 0.4 0.0 0.0 0.0
June 70.0 52.7 61.4 106 14/1961 43 01/1954 65.2 1958 57.8 1952 0.8 0.0 0.0 0.0
July 71.4 54.1 62.7 105 17/1988 44 29/1951 65.8 1992 58.7 1951 0.5 0.0 0.0 0.0
August 72.1 55.0 63.6 100 01/1993 45 30/1952 67.3 1993 59.7 1955 0.3 0.0 0.0 0.0
September 73.5 54.9 64.2 103 14/1971 41 30/1950 69.7 1984 60.1 1948 1.4 0.0 0.0 0.0
October 70.1 51.9 61.0 99 05/1987 37 20/1949 65.4 1992 57.0 1971 0.3 0.0 0.0 0.0
November 62.9 47.4 55.2 85 01/1967 31 30/1954 59.8 1950 49.9 1994 0.0 0.0 0.0 0.0
December 56.4 43.2 49.8 75 02/1958 24 09/1972 55.2 1958 44.9 1965 0.0 0.0 0.7 0.0
Annual 65.3 49.2 57.3 106 1961/06/14 24 1972/12/09 60.1 1958 54.7 1949 3.9 0.0 2.0 0.0
Winter 57.1 43.6 50.3 77 1986/02/26 24 1972/12/09 53.9 1959 45.0 1949 0.0 0.0 1.9 0.0
Spring 64.0 48.0 56.0 97 1984/05/27 31 1966/03/03 60.5 1992 53.0 1953 0.5 0.0 0.0 0.0
Summer 71.2 54.0 62.6 106 1961/06/14 43 1954/06/01 65.8 1958 59.4 1955 1.7 0.0 0.0 0.0
Fall 68.9 51.4 60.1 103 1971/09/14 31 1954/11/30 63.4 1958 57.4 1948 1.7 0.0 0.0 0.0

Precipitation

    Total Snowfall
  Avg. High Year Low Year 1 Day Max. >=
0.01 in.
>=
0.10 in.
>=
0.50 in.
>=
1.00 in.
Mean High Year
  in. in. - in. - in. dd/yyyy
or
yyyymmdd
# Days # Days # Days # Days in. in. -
January 4.40 11.26 1993 0.24 1991 5.59 04/1982 11 8 3 1 0.0 1.5 1962
February 3.61 13.64 1998 0.00 1953 2.92 02/1998 10 7 3 1 - - -
March 2.80 9.01 1958 0.05 1988 1.99 08/1978 10 6 2 0 - - -
April 1.37 6.36 1958 0.00 1949 2.30 02/1958 6 3 1 0 - - -
May 0.39 3.81 1957 0.00 1962 1.53 20/1957 3 1 0 0 - - -
June 0.11 0.86 1967 0.00 1949 0.81 02/1967 1 0 0 0 - - -
July 0.02 0.35 1977 0.00 1948 0.35 02/1977 0 0 0 0 - - -
August 0.04 0.66 1976 0.00 1948 0.56 19/1997 1 0 0 0 - - -
September 0.18 2.30 1959 0.00 1951 2.29 18/1959 1 0 0 0 - - -
October 0.99 7.30 1962 0.00 1959 2.64 13/2009 3 2 1 0 - - -
November 2.32 7.94 1973 0.00 1959 2.39 30/1973 8 4 2 1 - - -
December 3.75 12.30 1955 0.01 1989 3.16 11/1995 10 7 3 1 - - -
 
Annual 20.00 38.34 1983 9.20 1953 5.59 1982/01/04 64 38 14 5 0.0 1.5 1962
 
Winter 11.76 25.71 1998 2.71 1976 5.59 1982/01/04 32 21 8 3 0.0 1.5 1962
Spring 4.57 15.70 1958 0.26 2008 2.30 1958/04/02 19 11 3 1 - - -
Summer 0.17 0.86 1967 0.00 1956 0.81 1967/06/02 2 1 0 0 - - -
Fall 3.50 10.69 1972 0.05 1995 2.64 2009/10/13 12 6 2 1 - - -
California averages and extremes in precipitation and temperature and Top 10 U.S climate extremes.
Winter = Dec, Jan, and Feb Spring = Mar, Apr, and May
Summer = Jun, Jul, and Aug. Fall = Sep, Oct, and Nov
Data period is 1948 - 2010, San Francisco Airport. Source: Western Regional Climate Center