On a cold day, any moisture in the air inside your car — from passengers exhaling, snow on your boots, etc. While less problematic for auto glass than cold winters, summer's hot air and humidity may also fog up your windows. Pin On Products Old windows tend to develop condensation from moisture. Foggy car windows in summer . How to clear fog from windshield during summer. And we don’t want that because it’ll fog up the car’s windows. The window should look clear, with no streaks or residue. Heat on and windows open. These often get clogged up due to filth and leaves. — turns to condensation when it hits air next to the windows that's below a certain temperature, called the dew point. Use a paper towel to spread it evenly all over the glass. Defog car windows in summer if this first tip doesn’t work and your windows are having trouble defogging, apply the hot, dry air from the car heating system directly onto your windscreen. You may even want to roll down...