Weather in San Francisco for January?

In San Francisco you have to be ready for anything. It might rainy and windy, it might be sunny and soft like Summer. Or anything in between. Usually in between. Bring layers. You see lots of tourists doing outside things here even in relatively bad weather. Most of the time it's just a little chilly. Sweater weather.

It's San Francisco. It could be anything. Usually it'll be rainy and cool (40's in SF, can get colder outside of SF), might have days of fog so you never see the sun, might get fairly breezy which will make it feel colder. But then you can have a day that starts out foggy and then the sun breaks through and the temp goes up to 70, but then plummets after sundown. Or after just 30 mins the fog will roll back in and it'll get cold again. Can't be predicted. The weather people will say on the night news that it's going to be bright and sunny tomorrow but when tomorrow comes some rain storm has expressed in from Alaska and it'll be cold and rainy and ugly and you didn't bring your umbrella and got thoroughly soaked and now have a vendetta out for the weather people (ok, too much information). It's best if you dress in layers so if it does get warm you can take off a layer, or put more layers on as it gets colder. Come prepared for rain since January is in our rainy season.

Yes, it's nice outside if you wear layers. It can get chilly quickly, especially if the wind picks up or the fog comes in. Also, the rains begin in January, so come prepared.

Being on a boat is quite cold, so dress really warm.

Yes, it get chilling at night but it does not snow here. I think the best time to come to San Francisco is April and May, when it's not too cold or way too hot.