# How come you have to scratch when it’s not freezing?

If you have to scratch, it may not have frozen. Car windows can already freeze when it is still a few degrees above zero. So you have to scratch when it’s not freezing. How is that possible?

During a calm night with clear spells, the Earth’s surface cools and the air is also cooled. This happens from below. On clear nights with little wind, it can easily become five degrees colder at a height of 10 centimeters than at one and a half meters (the official observation height). And then you may have to scratch when it’s not freezing. We explain below how that works.

## Scratching when it’s not freezing – a mystery?

Not only the earth’s surface loses heat at night, but also cars. These often cool more strongly than the air around them. The windshield of the car becomes colder than the air and begins to cool the air above it. Colder air can contain less moisture and as a result, droplets will eventually form, making the car window wet. If the glass then cools to below zero, these droplets freeze and form an ice layer, so you have to scratch while it is not freezing. And then you need the ice scraper to regain sight. Or you look at these tips to get the window clean again.

## Big frost without ice on your window

Ice can therefore form on the car window if it does not freeze at normal height. It is also possible that the windows do not always need to be scratched when it is freezing. If the air is very dry, it can freeze considerably without ice forming on the car windows. There is simply no moisture to make ice. Even when it freezes while it is cloudy, the ice formation is often not that bad, because the car window then becomes little or no colder than the air above it.

## Watch out for ice on the inside of the window

If the car itself is cold, the moisture can also form ice on the inside of the car. Do you recognize that? Just scratched, you start the car and drive away. Then the inside of the window is full of ice. Then you see nothing again. There is nothing for it but to clean the inside of the window. It is more convenient to prevent a layer of grease from forming on the inside of the window. For example, by regularly wiping the window with an anti-condensation cloth.

– Thanks for information from Autoweek.nl