Well, not the desert southwest, but I deal with bangers interspersed with occasional rainy days and sunshine in the rockies up here.

I'm not fond of chaps, but then again, I'm generally ok (in the summer) wearing quick drying nylon pants on my bottom. if it really gets cold and horrible I make camp or pitch my tarp and hammock and warm up - but it's pretty rare for me to need/want to do that even
in the worst of weather as long as I am moving. So, my general stuff for this is a windshirt,
treated with nikwax. this is enough to repel most light rain and stuff. I then carry an integral designs SilPoncho, which if it gets foul comes out and goes over me and my pack, with the shockcord then looped around me to snug it up - Open arms, so no need for pit zips, but good protection.