2000 buick

Wet carpet only on rear right passenger side after it rains. Help
how do I fix it?

Hmm, remove the rug dry it out, have someone spray down the car, you are inside, of course, see where it comes in.

if you have a roof rack on it sometimes they leak around the mounts. if not its probably the door or window seal on that side or rear window seal. like max said have someone turn a hose on the car while your inside looking for where its coming in