Definitely rain pants in the PNW, where, when if it's not raining, you'll get soaked to the waist from dew or rain on brush, which we have a lot of! Most trails are brushed out only every 3-5 years (or longer) because of greatly decreased trail maintenance budgets. The brush grows a lot faster than that!

You may find the same problem in the Rockies, especially at lower altitudes where the grass and brush are taller.

One more item for the Rockies--plan to do most of your hiking up high (but allow time to acclimatize on the way), because at lower altitudes where lodgepole pines predominate, most of the trees are dead from the bark beetle. Especially watch where you're camping in these dead tree areas--you are pretty much forced to camp out in meadows, like it or not, for your own safety. In those areas I try to pitch the tent at bedtime and take it down before breakfast in hopes of reducing the effect on the vegetation under and around the tent. There's still plenty of outstanding scenery, though, especially up in the alpine areas! I notice and mourn the dead trees going in, forget about them up in the alpine and don't really notice them on the way out (probably because I'm remembering the beauty of the alpine areas).