I once had a really nice (NorthFace or Sierra Designs or similar) red ripstop nylon poncho. I got it cheap at a garage sale like I do with much of my stuff. Anyway, the back pack it and most of my other valuable gear lived in was apparently desparately attractive to one of the bros here in SoCal that work at the carwashes. Anyway, he got to enjoy it for awhile until probably one of his other bros decided they needed it more than him.

Now, I keep two folded up huge industrial trash bags in my pack in case the bros need replacement ponchos. I always have my baseball cap on as a "rain hat".