What is the "cold" temperature for tire inflation?

Ambient air temperature in the shade. Unless you have issues with your brakes, bearing, or alignment, your tires will only heat up 5-10 degrees above the air temp when driving and the pressure will usually increase less than 5 psi. Tire manufacturers account for this when they determine the "cold pressure". However, tires facing the sun will get warmer than those in the shade. If you're parked on asphalt the tires, in the sun, will get hot and cool down when driving so don't rely on that "hot" temp.