San Francisco averages 4.1 days a year above 90°F, with December the wettest month at 4.76 in of normal rain. The hottest day on record was 106°F on Sep 1, 2017; the coldest, 28°F on Dec 22, 1990. The single biggest 24-hour rain event recorded was 5.54 in on Nov 5, 1994.
Climate and Average Weather Year Round in San Francisco
Year-round temperature
In San Francisco, the warmest months are June, August, September, October, with average daily highs between 67°F and 70°F. The coldest stretch runs December through February, with highs between 58°F and 60°F and overnight lows reaching 47°F.
Rainfall through the year
Rainfall in San Francisco averages 1.9 in per month over the long run. December is the wettest at 4.8 in, while July is the driest at 0.0 in.
Days at 90 °F or hotter
San Francisco averages 4.1 days per year at 90 °F or hotter. The hottest year on record saw 8 such days (2003); the coolest just 1 (1994).
Precipitation this year
As of May 28, San Francisco has received 11.1 in of precipitation this year — 22% below the long-term normal for this point in the year (14.2 in).