I live in PNW too. In my opinion the biggest problem in wet weather is how dirt my dog gets in his underbody. He gets muddy, wet, twigs get stuck on his legs...
Last month I got my rough collie some pants! We get a lot of looks on our walks ( when it's wet and muddy) but I'm happy that he is not dirty. If it's only wet/muddy outside he wear his "pants", if it is raining I add a simple rain poncho. The pants I got from Amazon, the poncho at the local pet store.