There is a reason San Franciscans dress like they are expecting an argument with the weather. The city sits where cold ocean air meets warm inland valleys, and the result is fog so reliable it has a name, a personality, and a devoted following online: Karl.
Karl rolls in over the hills most afternoons and can drop the temperature ten degrees in the time it takes to finish a coffee. A sunny morning in the Mission can become a grey, wind-whipped afternoon out at the coast — sometimes on the same walk.
Every local half-believes the line about the coldest winter being a summer here. The fog has earned it.
What to actually pack
Layers, and then one more than you think. A light jacket in a day bag is the local uniform, worn by people who have been caught out too many times to risk it. Check which neighbourhood you are headed to as much as the forecast: the east side bakes while the west side shivers, and the hills in between make their own rules.
