Hunker down and look out the window. Seattle in the winter is that wet sort of cold. But on the plus side they got some of the best donuts and baked goods around. So at least you wont be disappointed in what you're eating while you're stuck inside.
The Seattle aquarium is always a good visit. Been out of the area for a while but when I grew up the family would plan on a day into Seattle, we lived out in the Kent/Renton area, and depending on the weather we would either go to the Woodland park zoo, aquarium or Science center. The woodland park zoo is even getting some good indoor exhibits so that you don't have to spend the whole time outside.
Because it seems unlikely anyone else will mention it, I'm tapping my bigleaf maple trees and freezing the sap for steam-boiling later this winter. You can tap maples, alders, birches, and I've heard tell about tapping willows and cottonwood, too. The bigleaf sap is a little lower in saccharides than sugar maples, but it makes dandy, delicious syrup.