Why do car windows freeze even when they haven’t frosted yet?

For ice, of course, you need water. Rainfall can freeze on a supercooled object, and so can water vapor. When it is cold enough and the air contains enough moisture, water vapor can turn into ice.

This transition can occur instantly, directly from water vapor (a gas) to ice, or through sublimation, giving you frost formation ride a car. Your car will sparkle a little, but this frost is very easy to remove. In fact, these are ice crystals that instantly settle on the car, but you can also easily wipe them off.

The most stable variant occurs when water vapor first condenses on the car, i.e. moving from water vapor to liquid water, and only then freezes. In this case you get a white and harder layer of ice on the car,”rhyme”It is less easy to remove.

So the first condition is the presence of sufficient moist air. When dry ground air is provided, with low relative humidity, the car window will not freeze.

The second condition is temperature. The car window will freeze if the temperature is 0°C or less. The negative temperature is usually reached by an object faster than the surrounding air. It is true that the car, which is also made of metal and glass, will cool faster than the surrounding air. Horizontal car parts in particular will lose heat faster. The roof and windshield will cool and freeze faster than the side door.

Therefore, even at positive air temperature, the temperature of the car windows can already be negative and condensation and frostbite can occur. This is why car windows can freeze as soon as the mercury drops below five degrees Celsius.

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So when the weather forecaster is forecasting a temperature of 3-4 degrees or lower and the supplied air is not coming from the dry east direction, you should start ringing the bell from now on.

Do you have a question about the weather? Then ask them to Itherman Bram.

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