As winter approaches, many motorists will experience a low-pressure warning light on the dash or simply observe that the tires look a bit less full than they should. The main reason for this is the dropping temperatures, which cause the air to become denser and consequently lower the tire pressure. Of course, tires naturally lose pressure over time, and there can be a puncture.

Tire pressure monitoring systems (TPMS) are a real boon to safety and convenience, and they have been required on all new cars since September 2007. By triggering a dashboard light to let you know when one or more tires is low on air, TPMS can take the guesswork out of wondering whether a tire is low.

Colder temperatures will cause tire pressure to drop about 1 psi for every 10°F drop in air temperature. Getting a tire pressure warning light on a chilly morning doesn’t necessarily indicate a puncture, just that your tires are running low pressure and you need to top them off as soon as possible. Drive a few miles and the tires will warm up, perhaps causing the warning light to turn off. Whether it goes off or not, your tire pressure needs to be checked with a gauge and topped off. This is a simple DIY chore, or you can ask a mechanic to have a look. (See our tire pressure gauge buying guide.)

As a general rule, check the pressure monthly. Don’t wait for the tire pressure warning light from to come on.  It’s meant to alert you of a tire losing air while you're driving, not serve as a maintenance reminder.

Even if your vehicle is equipped with TPMS, our recommendation is to use a gauge to check the pressure in all of your tires at least once per month, no matter what the weather is like.