It is still warm in the Bay Area at that point in time. It depends on if there is a heat spell or not at that time, but I would say it will probably be in the low 70s or upper 60s in San Francisco. It gets cool at night, so bring layers.
My b-day is Sept 29 and it always seems to be above 85 degrees on that day, but I'm not in SF.
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Veni, Vedi, Visa.
I came, I saw, I did a little shopping.
I was in SF last year in late Sept/early October and the weather was just how Zeitgiest described it - it was a beautiful time of year to visit. There was no fog and it was sunny the whole time.
When I visited SF a few year ago in August, I froze my a$$ off. It was sprinkling also. Compared to OC I thought it was cold. Perhaps girls that live there can give you a better answer.
I've lived in the Bay Area most of my life, and San Francisco will ALWAYS have fog. It may burn off at some point, and you may get lucky with some nice sun. But at some point in the day I have always needed a sweater, whether it was summer, fall, or spring. It can also be windy. I would say bring clothes covering weather conditions ranging from mild spring weather to cold wind and fog.
I am kinda late but I may be a wimp cuz I grew up in sunny L.A. my whole life, but I also froze my butt off last year, late July. It's nice in the day, but it gets really chilly at night and in the am, so I would take a sweater or light jacket.
I'm in WI so it might not feel too cold for me :) I want the weather to be beautiful but if the nights get cool I get to bring my new poncho...I could use an excuse to wear it.