🌉 San Francisco Weather

The city the fog built

San Francisco breaks every rule about California sunshine. Thanks to the cold California Current offshore and its perch at the mouth of the bay, the city has cool, foggy summers and mild, damp winters — the famously chilly summer that locals have long (if apocryphally) attributed to Mark Twain. The fog is such a fixture that residents have nicknamed it "Karl."

Summer fog season

Counterintuitively, the foggiest, coolest time is summer. As California's interior heats up, it pulls cold marine air and fog through the Golden Gate, and July highs barely reach the low 60s°F (around 17°C). Neighborhoods just a few miles apart differ sharply — the Sunset District can be socked in and windy while the Mission basks in sun.

Mild, green winters

Winter is actually the warmest-feeling season in terms of sunshine, though it brings the rain. Highs stay in the upper 50s°F (around 14°C), frost is almost unheard of, and the hills turn green. Most of the city's 23 inches (580 mm) of annual rain falls between November and March.

True heat is rare and brief, arriving only during autumn offshore-wind events. For much of the year a jacket is the essential San Francisco accessory, even in July.

Fog, microclimates, and no real summer

San Francisco's summers are famously cool and foggy — the Pacific's cold current and the inland heat draw a thick marine layer through the Golden Gate, so July can be grayer and chillier than April. The saying 'the coldest winter I ever spent was a summer in San Francisco' captures it.

The city's hills and exposure carve out dramatic microclimates: a sunny Mission District afternoon can sit 15°F (8°C) warmer than foggy Sunset just a few miles away. The warmest, clearest weather often comes in September and October, after the summer fog machine finally winds down.