San Francisco's Mediterranean climate is famously deceptive, with cool summers that confound visitors expecting California sunshine and mild winters that rarely require serious insulation.

Rain arrives almost exclusively between November and March, making waterproof layers essential in winter but largely unnecessary from late spring through early autumn.

Temperatures hover between 10°C and 21°C year-round, with the coldest mornings in January and the warmest afternoons in September and October, though true heat is rare.

Persistent wind and fog roll through the city's microclimates unpredictably, particularly in summer when the marine layer blankets western neighborhoods while the Mission bakes.

The famous fog means layering isn't optional philosophy but survival strategy—you'll shed and add clothing multiple times in a single afternoon.