So we spent some time in Port A last week. While leaving we noticed a lot of sand and stuff on our cars - figured it was salty humid air stains/water spots or something. Took it to a car wash and the paint on the car looks fine but the guys could not get the spots off the windshield with their normal glass clear and a rag.

What's the secret here? Vinegar? Something else?

I tried vinegar and it does indeed look like it cleared it up but not 100% and not at certain angles in the sun...

Might want to post on the Outdoors board. This one doesn't get much traffic.

Spots are hard water/salt deposits, keep using the 50/50 water/vinegar solution and let it sit there for a bit before going after it with a brush.