Source of Water Leak... on 1995 Pontiac Grand Am

My Grand Am GT is leaking on the passenger side only, and if it's really wet, the rear seat floor on the drivers side gets a little damp. I don't know where the leak is coming from, but my best guess is either a vapor barrier issue on one of the doors, or a body drain (weeper tube?) clog in the front of the car. The car only gets wet when it rains, so it is not the heater core/AC, and to further prove that, it is confirmed to be water that accumulates on the floor, not heater core fluid.

Thanks!

2 answers
find leak to fix
poss leaking windshield have it inspected to confirm leak.