Tire Pressure in Cold Weather: Why It Drops and How to Check It

This guide is for drivers who saw the tire pressure light come on during the first cold morning, or who want to check their tires before winter.

The first cold morning of the season often turns on the tire pressure warning light. That’s not a coincidence, and the fix is usually a few minutes at an air pump.

The quick answer

NHTSA says that as the outside temperature drops, so does tire inflation pressure.¹ Check your tires when they’re cold, meaning the car hasn’t been driven for at least three hours, and inflate them to the pressure your vehicle maker recommends.^1,2

Where to find the right pressure

NHTSA says the recommended pressure is on the Tire and Loading Information label on the driver’s side door edge or door post, and in your owner’s manual.² The number molded on the tire sidewall is not the recommended pressure for your vehicle.² FuelEconomy.gov gives the same warning: don’t use the maximum pressure printed on the sidewall.³

How to check and fill

NHTSA’s steps:²

1. Find the recommended pressure on the label or in the manual.
2. Check all tires, including the spare, with a tire gauge.
3. If a tire is too high, let air out slowly by pressing the valve stem.
4. If a tire is too low, add air to reach the recommended number.
5. Make sure all tires match, unless the front and rear pressures are specified differently.

Our advice: keep a simple gauge in the glove box. Gas station gauges are often worn or damaged.

Don’t rely on the warning light alone

NHTSA notes that tire pressure monitoring systems warn only when a tire is significantly underinflated, and that underinflated tires are hard to spot by eye. It recommends inspecting tires monthly with an accurate gauge.²

Why it’s worth the trouble

FuelEconomy.gov says keeping tires at the proper pressure can improve gas mileage by 0.6% on average, up to 3% in some cases, and that under-inflated tires lower mileage by about 0.2% for every 1 psi drop in average pressure.³ Our advice: correct pressure also helps the tire grip and wear evenly.

Checklist

• Check pressure monthly, with the tires cold.
• Use the number on the door label, not the sidewall.
• Include the spare.
• Recheck after a big temperature drop.
• While you’re there, do the penny test.