Getting Rid of Water Spots on Windshield?

Back in the summer when it was 100+ F, while watering my lawn the water got on my car windshield and left a residue that I cannot get off. I've tried SLR, LimeAway, Crudcutter, Goo Gone, and RainX.

Does anyone have a suggestion as how to get this residue off my windshield?

By Wayne from Huntsville, TX