Fortunately, you've got actual locals to advise you.
I spent August in SF many years ago and, being from the South, was in disbelief (and cold!) a lot. I had brought one trench, one sweater, a vest--otherwise more warmer-weather items. I lived in the sweater and trench!
Sounds like you have a grip on the actual temps, and you do layers--is it that you are trying to turn that into more polished work-wear, or develop better capsules so you have good, convenient options ? Do you need some clothing that looks more cheery for "summer" but still has the necessary warmth--like sweaters in brighter colors or coats and toppers that are your "summer coats" you don't wear as much in winter? Maybe you need toppers that are more comfortable for all-day wear, as opposed to in warmer weather, I may wear a jacket just for polish to get to and fro, but take it off during the day. There was a discussion recently on the problem of finding really comfortable jackets, or like knits, ponte, sweater-blazers, and so on. And I like the idea of undergarments when the temps stay cool all day and you don't have to un-layer, because that stretches the season of wear of some items--I'm trying to do more of that so that I can wear some of my favorite, good-quality items more often--2-3 season wear.