This is known as Charles's Law. As a gas warms, it expands - the volume increases, thus creating more pressure. In reverse, as it cools, it looses volume and there is less pressure.
The mere fact they expanded 5psi in a 40 degree temp change just sitting would indicate to me to check the pressures just before I left, so as to not have the pressure expand too much once on the road. Being a race fan, you know tire temps can adversely affect tires and tire wear.
"Sunny" the 2017 Sunseeker 3010DS
2006 Jeep Liberty Toad
.... and lovin' life...