As the temperature drops, so does your tire pressure
For every 10 degrees the temperature drops, the PSI in your tires will drop approximately by one. This is due to the simple relationship (ideal gas law for the scientific crowd) of pressure and temperature.
As the temperature drops, the air molecules contract.
These smaller air molecules can then escape the tire. This is especially the case with air pumps that use the air that we breathe. Some places will use strictly nitrogen which will help prevent the air from leaking.
Nearly every car should have the manufacturer's recommendation for the tire pressure listed as the "cold air tire pressure." This is what the tire pressure should be during the cold winter months.
Most modern cars also have a dashboard light called the Tire Pressure Monitoring System (TPMS) which will warn the driver when the tire pressure is too low.
TPSM was actually mandatory for all new vehicles starting in 2007. This light will come on when the tire pressure drops below 25 percent of the manufacture's recommendation. When the light comes on, it's already a danger.
“When the light comes on, take it to your tire guy and have it checked out,” said Peter Steinkoenig, manager at Quincy’s Delta Tire. “Some people like the lights, some people don’t. Sometimes it's just to air up your tires and you're OK until the next time it gets cold.”
Experts recommend checking the tire pressure monthly in the winter. Having low tire pressure will negatively impact fuel efficiency, risk poor control handling of the vehicle, and in the worst case, cause a blowout which could cause a crash.