Just to add another possibility, which has worked for me for 40 some years, but is not real popular given the dominance of "breathable" water proof fabrics.
Back in the day, I started with a nylon poncho and chaps. Today I use an MLD set of cuben poncho and chaps – much lighter! I've used them (poncho and chaps in whatever fabric) in the Cascades, the Rockies and the Sierras, and they've never let me down. Yes, the poncho can blow around, but a waist belt of cord or light bungie readily solves that problem. The poncho can act as an emergency shelter, or a tent/tarp extension. Or even a ground cloth. It also acts as a pack cover, preventing any rain from getting into or onto the pack. It does not build up wet sweat in my clothes, since there is so much air circulating under the poncho. If wearing shorts, I don't bother with the chaps.
They are not "ideal" above tree line, due to blowing, but with a waist cord, I haven't really had any problem.
The MLD cuben set is incredibly light weight.
YMMV.

