Why Does Frost Form on the Inside of Car Windows?
2 Answers
Frost forms on the inside of car windows due to the temperature difference between the interior and exterior of the vehicle. When the temperature inside the cabin is higher than outside, moisture in the air condenses on the inner surface of the windshield, forming frost. As warm, moist air comes into contact with the colder glass, it cools down, causing the moisture to condense into frost on the glass. To address frost on the inside of the windows, first turn on the air conditioning and use the cold air setting for a while until the frost dissipates. Then switch to the heater and adjust the vents to direct warm air toward the windshield. The warm air will help evaporate the frost. Alternatively, you can use a cloth dipped in dish soap or a specialized anti-fog solution to wipe the inside of the windshield, which can effectively prevent fogging and frost formation.
I often drive my kids to school and find the issue of frost forming on the inside of the car windows quite annoying, especially on early winter mornings when the entire windshield gets covered with a layer of frost, blocking visibility. This usually happens due to excessive humidity inside the car—like when the kids' water bottles spill, their backpacks aren't dried properly, or moisture gets in from opening and closing the doors on rainy days. The low temperature inside the car cools the glass quickly, causing the moisture to condense and form frost. Poor air circulation also traps exhaled water vapor, making it accumulate even more. There have been times when the frost kept building up while driving, forcing me to pull over and wipe it off for a while. To prevent this, I usually crack the windows open for a few minutes before getting in to ventilate and reduce humidity. Once the engine warms up, I turn on the air conditioner in dehumidification mode to blow on the glass, which solves the problem. Never use a hot towel to wipe the frost, as it may crack the glass. Most cars now come with a one-touch defrost function, but taking preventive measures early is much more convenient.
