Tire pressure changes with temperature at roughly 1 PSI per 10°F. A 30°F temperature drop overnight (common in fall) reduces tire pressure by 3 PSI.
Most TPMS sensors warn at 25% below the manufacturer spec. If tires were set at 35 PSI in summer and drop to 32 PSI in fall, you're at 91% of spec — close to the warning threshold.
Fall is when the TPMS light comes on for most drivers. Many drivers panic about a tire failure when they actually just need to top up pressures.
The fix: check pressures monthly through fall and winter, top up to door-jamb spec, drive 5–10 miles to clear the TPMS warning.
If the light stays on after topping up, that's a different issue — slow leak in one tire, TPMS sensor failure, or significant pressure imbalance.