Outerwear options are limited when the elements force us to be practical. For instance, as much as I want to sport a blazer and harness, a raincoat is more appropriate if I have to ride the bus to work on a rainy day. The randomly changing "earthquake" weather of San Francisco has trained me to layer like a pro and prepare for anything with these key pieces.
My San Francisco elemental essentials: Boots, light-weight and water repellent outerwear, wool coat/cape, leather high-tops, water repellent bag. I think you can tell if someone is native to SF if they always bring a sweater just in case (or maybe that is a Filipino thing?).