Why scratch your car window in the morning, even if it’s not freezing | Explanation – science

Ice forms on our car windows when it starts to get cold at night. During the day, the sun heats the surface of the earth and everything on it and the layers of air above it. But as soon as the sun disappears behind the horizon and night falls, everything loses its warmth again. How fast this is depends on the weather. For example, heavy cloud cover and a lot of wind will slow the process.

When the temperature drops further than that and reaches the freezing point, the water film on your car window turns into lots of scratching fun.

Martin Peters

During this cooling, your car window goes from completely dry to covered in a layer of icing. The colder the air, the less water the air can hold. As a result, the air becomes saturated with water vapor. Then one talks about 100 percent humidity. This water has to go somewhere and droplets gradually appear on cold surfaces like your car. When the temperature drops further and reaches the freezing point, the water layer turns into a lot of crab fun. But if there is not enough moisture in the air, your car windows will still be clean even at a few degrees below zero. This is “dry frosting”.

However, you sometimes find yourself scratching at the snow in the morning while the thermometer reads a positive temperature. How is this possible? It can cool your car faster than the surrounding air, so your window temperature will reach below freezing point more quickly. However, you can prevent this by, for example, placing the car near a building or under a roof. Your car then loses heat less quickly, so you don’t have to scratch in the morning. You can also always use a protective cover to prevent icing on your windows.