On my WA state tour, self-supported, I had a pair of thin tights (over shorts), a pair of the nylon trekking trousers mentioned above, and some cheap rain pants. I actually cycled in freshly falling snow on the higher North Cascade passes. Some combination of the above always worked. One good trick I had learned from someone earlier was that you should be able to wear everything you carry at the same time, where everything functions as a layer.

And don't forget the "bagtex" trick--(empty) bread bags for the feet, inside the shoes, over the socks.

PS: I plan on hiking over the Olympics from the Sound in August, ending with a coastal trek. That's beautiful country and I'm looking forward to it. Enjoy!