Why does tire pressure drop in cold weather?
Tires lose about 1 PSI for every 10°F drop. Why it happens, why the light comes on in the morning, and what to do (without overinflating).
The first cold morning of fall, the tire pressure light comes on. By afternoon it's off again. Nothing is broken and nothing is leaking: your tires really did lose pressure overnight, because the air inside them got cold.
The short version: tire pressure drops about 1 PSI for every 10°F the temperature falls. Fill your tires to the number on your door label, checked on a cold morning, and keep checking through winter.
Why tire pressure drops when it gets cold
Air takes up less space when it's cold. Inside a sealed tire, that means the same air presses outward less, so the gauge reads lower. Les Schwab puts it simply: the drop isn't air escaping, it's the air inside the tire contracting.
How much? Discount Tire and Les Schwab both use about 1 PSI per 10°F. Goodyear says 1 to 2 PSI. Here's what that looks like for a tire set to 35 PSI on a 70°F day:
| Outside temperature | Approximate pressure |
|---|---|
| 70°F (when you filled it) | 35 PSI |
| 50°F | 33 PSI |
| 30°F | 31 PSI |
| 10°F | 29 PSI |
| −10°F | 27 PSI |
That's with no leak at all. If a tire was already a couple of PSI low, a cold snap can push it past the point where the warning light comes on.
Why the light comes on in the morning and goes off later
The tire pressure light turns on when a tire is about 25% below the pressure on your door label. For a car that calls for 35 PSI, that's around 26 PSI. Overnight is the coldest part of the day, so that's when a low tire crosses the line.
Once you drive, the tires warm up and the pressure climbs back, and the light can go off by the afternoon. That doesn't mean the problem fixed itself. The tire is still low and the light will be back the next cold morning. More on what the tire pressure light means.
What to do about it
- Check in the morning, before driving. That's when tires are cold and readings are accurate. Our guide to checking tire pressure walks through it.
- Fill to the number on your door label. It's the same in winter and summer. There isn't a separate winter number.
- Don't overinflate to make up for the cold. Les Schwab warns that going above the recommended pressure can reduce traction, hurt handling and wear tires faster, which is the opposite of what you want on icy roads.
- Filling in a heated garage? Tire Rack's rule of thumb is to add about 1 PSI for every 10°F colder it is outside than in the garage, so the pressure is right once the tires cool down outdoors.
- Check again after big temperature swings. Discount Tire recommends a check after any sharp rise or drop in temperature, and Les Schwab suggests once a month through the colder months.
Where to get air in cold weather
Gas stations known for free air include Wawa, Sheetz, QuikTrip and Kwik Trip, and every gas station in Connecticut (and in California, for customers who buy fuel) has to provide free air by law. Outdoor machines can be busy or out of order in deep cold, so it helps to know a backup. Tire shops like Discount Tire and Les Schwab check and fill tires for free during store hours. To find the closest option with hours and driving time, search the free air map.
And in summer?
The same thing happens in reverse. Tires gain pressure as it gets warmer and as they heat up on the highway. That's normal. Don't let air out of hot tires to get them back to the label number; check them again when they're cold.
Low on air right now? See the closest free air, open now, with driving times. Find free air near meQuestions
Why does tire pressure drop in cold weather?
Cold air takes up less space, so the air inside the tire presses outward less. Nothing is leaking. Tire makers put the drop at about 1 PSI for every 10°F the temperature falls (Goodyear says 1 to 2 PSI).
How much does tire pressure drop in cold weather?
About 1 PSI per 10°F. A tire set to 35 PSI on a 70°F afternoon will read around 31 PSI on a 30°F morning. Discount Tire notes that a warm afternoon followed by a cold night can leave tires 5 to 10 PSI lower by morning.
Should I put more air in my tires in winter?
Fill to the same pressure as always: the number on the label on your driver's door frame, checked when the tires are cold. Don't go above it to make up for the cold. Les Schwab warns that overinflating in winter can reduce traction and speed up wear. The one exception: if you fill up in a heated garage, add about 1 PSI for every 10°F colder it is outside, so the pressure is right once the tires cool.
Why does my tire pressure light come on in the morning and go off later?
The cold overnight air drops a slightly low tire below the warning point. As you drive and the day warms up, the pressure rises again and the light can go off. The tire is still low, so add air.
Is it safe to drive with low tire pressure in the cold?
A short drive to get air is usually fine if no tire looks flat. Low pressure hurts grip and braking, which matters more on cold or snowy roads, so fill up soon.