I keep saying we're in this transition period between winter and spring, but truth be told, we're still pretty immersed in winter. I think we should prepare for a wet spring, should it ever arrive. 

But in the spirit of the eventual transition, jackets and raincoats are your best friend. We're at least moving out of the need for our full length down coats. Sweaters under raincoats are a great way to layer and stay warm/dry. Even throwing a shorter jacket under a longer raincoat is a great option.
The rumor is Seattleites don't use umbrellas, which is sort of true, but we do have killer raincoats: Pipe + Row.