What should I pack for San Francisco?

San Francisco's weather will trick you if you pack based on "California." The city sits on a peninsula where Pacific fog pours through the Golden Gate strait most mornings from June through August. Step off BART at Embarcadero station and the damp cold hits your face immediately. Temperatures hover around 12-15°C in the fog belt. That same afternoon, the Mission District might reach 21°C under clear sky. Pack three layers minimum. A wind-resistant shell is the single most important item you'll carry. Under it, a fleece or merino mid-layer for west side neighborhoods like the Sunset and Richmond. Underneath, a long-sleeve base that works alone when sun breaks through in SoMa around 2 PM. Cotton is a poor choice. The fog is wet enough to leave a film on your skin during the 1-km walk from Fort Point to the Golden Gate Bridge vista point. Synthetics or merino dry in an hour. Cotton stays clammy all day.

Footwear matters more in San Francisco than in most American cities. Filbert Street between Hyde and Leavenworth tilts at a 31.5% grade. Even the walk from Union Square up to Coit Tower in North Beach involves 90 meters of elevation gain over 1.6 km. Flat sneakers with no grip will slide on the smooth concrete sidewalks when fog makes them slick. Bring shoes with actual tread and ankle support. Forget sandals for the first 3 days. Alcatraz Island's cell house tour covers about 2 km of uphill concrete paths in steady wind, and the return ferry leaves whether your feet are wrecked or not. If you plan to walk Golden Gate Park end to end, that is 5 km on flat ground, but the trails through the botanical garden get muddy after overnight fog.

Skip packing an umbrella for a summer visit. San Francisco's rain falls mainly November through March, and the summer fog is not rain. It is a horizontal mist that makes umbrellas useless. Wind at the Golden Gate Bridge will invert a cheap one in about 4 seconds flat. What you need is a packable rain jacket with a hood. To be fair, the city's Walgreens stores on nearly every third block carry most toiletries at roughly the same prices you'd find at home. Sunscreen at the Walgreens on Powell and Market runs $9-12 for SPF 50. You will need it on clear days. The fog burns off by noon on maybe 40% of summer days, and UV at this latitude is strong enough to redden fair skin in 25 minutes. Bring your own prescription medications, though. US pharmacies require a local prescription for many items Europeans buy over the counter.

September and October are San Francisco's actual warm months, when temperatures reach 22-26°C and Dolores Park in the Mission fills with locals in t-shirts. If you visit then, swap the fleece for a light cardigan and add sunglasses you won't mind losing. November through March, pack proper rain gear. The city receives about 500 mm of rainfall across those 5 months, and the wind makes a hood non-negotiable. January nights average 8°C, cold enough for a proper winter jacket if you plan to eat outdoors in North Beach, where restaurants line Columbus Avenue with heat lamps that don't quite reach every table. One year-round item people forget is a portable charger. Navigate from the Haight through the Castro to the Mission on Google Maps and your phone battery hits 15% by 3 PM.