Ever wondered why the windows in your car get fogged up and how to stop it from happening? Car windows fog up when water condenses on them. It can happen inside and outside of the window. Water will condense on a surface if the temperature of the surface is below the dew point of the surrounding air. In other words, warm, humid air next to a cooler surface creates a foggy environment. So, when you go out to the car in the morning with foggy windows, it is because the air in the car is warmer than the air outside of the car. As a result, moisture will condense on the inside of the windows. For those of us in cold environments, dry rags, the car's defroster, and the handy tip in this video can help to eliminate your foggy windows.