If your tire-pressure warning light pops on during the first cold snap, it is usually just physics: tire pressure falls roughly 1 PSI for every 5 degrees C drop in temperature. A 20-degree overnight plunge can easily drop you below the warning threshold without any leak at all.
- Pressure drops about 1 PSI per 5 degrees C (roughly 1 PSI per 10 degrees F).
- A cold morning can trip the TPMS light with no actual leak.
- Top up to the door-jamb spec (not the number on the tire sidewall).
- If the light returns within days, you likely have a slow leak — get it checked.
The physics in one line
Air contracts as it cools. As a rule of thumb, every 5 degrees C drop pulls about 1 PSI out of your tires. Go from a mild 15-degree afternoon to a minus-5 morning and you have lost roughly 4 PSI across the board — often enough to trip the TPMS light.
What to do
Top your tires up to the door-jamb pressure, ideally when they are cold (before driving). Do not inflate to the big number on the sidewall — that is the tire's maximum, not your vehicle's target.
If the light clears and stays off, it was just the cold. If it returns within a couple of days, treat it as a possible slow leak and have it checked before it becomes a roadside flat.
Why does my tire light come on in the morning and go off later?
Cold overnight temperatures lower your tire pressure enough to trip the sensor; as the tires warm up from driving (and the day warms up), pressure rises back above the threshold and the light goes out. It is normal in late fall, but you should still top up to spec.
What pressure should my tires be?
Use the number on the sticker inside the driver's door jamb (or in your owner's manual) — that is the vehicle maker's spec. The higher number molded into the tire sidewall is the tire's maximum, not your target.
When is the pressure light a real problem?
If the light keeps coming back within a day or two of topping up, one tire is likely losing air through a puncture, a corroded rim seal, or a failing valve. Bring it in — a leak check and patch is quick and inexpensive.
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