Wear what you have to, and keep a bag in the car, it's the only option. I carry a pair of grey fatigues in my car, with a pair of wool long johns. A tshirt, a wool shirt and a rolled up poncho with liner. Two pairs of socks. I also keep a spare pair of work clothes in there, a pair of sweat shorts, a small light weight blanket and shave-and-shower stuff, in case I have to crash on a friend's floor some reason.

Most "problems" last 24 hours. It's easier bugging a friend than sleeping in the car, and warmer. And if it goes longer, well, that means I can clean (some of them are worse slobs than I am :P ).