Tire pressure in cold weather: why the warning light comes on the first minus 10 morning

The pressure light that comes on the first cold morning is almost never a puncture: it is the physics of air contracting.

Understand, check, correct

The air in a tire loses about 1 psi every time the temperature drops by 5 to 6 degrees Celsius. A tire inflated to 35 psi on a 15 degree day therefore reads around 30 psi on the first night at minus 10, and most TPMS systems light up at 25 percent below the recommended value.

Always check pressure cold, meaning before driving or after three hours parked, with a gauge and not by eye. The target value is on the driver's door jamb label; the number moulded on the sidewall is the maximum pressure, not the operating pressure.

If the light stays on after correct inflation, a sensor may be at the end of its life (the battery lasts 7 to 10 years) or your winter wheels have no sensors recognized by the vehicle. An installer reads the sensors in minutes and can program them during the seasonal changeover.