Weather Whys: Why does tire pressure drop on cold days?

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It happens all the time – a cold front moves in and your tire pressure light comes on. We all expect it, but why does it happen?

It all has to do with the space the air is taking up in your tire. Air is made up of molecules that are constantly in motion. When it is warm they move faster and the air expands, your tire pressure may even increase slightly on very hot days. When it is cold they move slower and the air condenses. For every 10 degree drop in temperature your tire pressure can drop about 1 PSI. That’s not a problem if it is just slightly cooler, we see temperature swings between day and night that don’t create a problem – but when it’s a strong front or storm that drops highs and lows 30 or more degrees, you’ll probably see your indicator light go off.

Driving on the tires warms them back up, this might cause your light to go off temporarily, it’ll come back on after you stop driving for a while and your tires cool back down. A cold day isn’t usually something to worry about, tire pressure will usually return to normal when the cold air moves out. When it gets cold and stays colder, Fall and Winter, you’ll need to adjust and add more air to account for the constant colder weather.

It’s in your benefit to do so too! Low tire pressure increases stopping distance and lowers your gas mileage.

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