My second 1965 Dodge Dart.

Time for windshield wiper seals. Also water can come in the bottom corners of the windshield. My best advice other than fixing the seals is to either have the car garaged during rain storms, or tarp it during rainstorms. Check your trunk spare tire well for water as well. Water gets past the old trunk seal as well.
The car I have outside, I just cover it with a nice tarp. Problem solved.