The important measurement is pressure, not temperature but as the pressure changes with temperature the only way to correctly measure the pressure of air in the tyre that air must be at the same temperature as the atmosphere surrounding it.
So, it doesn't matter what the ambient temperature is, just so long as the air in the tyre is at the same temperature.
Manufacturers factor in the the heat generated (above ambient) in the tyre by the amount of sidewall movement allowed by the inflation pressure.