I was driving last night (10:30pm) in Fremont, CA going home and I noticed my windshield kept getting foggy. I turned on the Defroster to max but it wasn't going away. After 20 min or so it started to build up from the center and slowly up. It was really bad. I then wiped my windshield with the wipers and it was all gone. But just within seconds it just started to build up outside again. I then had to keep turning on the windshield wipers every minute. I looked at other cars around me and checked the weather outside, but the other cars were just as fog free as my car and it wasn't that cold of a day nor was it raining. Please help on what may be causing this! I wash my car once a week so no I don't think it was because my car's dirty.