When I had my windshield replaced a couple years ago, the installation guy (a family friend - got a great deal on that one!) said I could spray and wipe a little WD-40 on the various rubber weatherstripping pieces to help them get watertight again. However, he did say that it was only a stop-gap fix - it swells the weatherstrip up for a while, but then it will dry out and shrink again, and the problem(s) come back.
But that's one quick fix, FWIW. HTH