Quote Originally Posted by X-Runner
Yeah well no shit that will fix it. But the spots are there every time it rains at work and do NOT come off with glass cleaner like you guys make it out to.
Until it's completely cleaned off and the glass is polished it will always come back. The rain is reacting with the junk that is stuck on the windows.

If it's really bad just get some Etch Cream from a hobby store. It's a really really mild form of hydrofluoric acid. It will take scratches and spots right off glass then you'll have to polish afterwards.