Low temperature doesn’t affect pcps much, I just fill the to the same pressure and shoot. But temperature differences can be bad for a pcp since air expands with higher temperature. The expansion of air is fairly linear and can therefore easily be calculated with the absolute temperature (the Kelvin scale) 0 degrees Celsius is 273,15 in Kelvin. So if I fill my pcp to 3000psi outdoors at 0 Celsius and the bring it inside to room temperature it will have 3200 psi - at 20 degrees Celsius (from 0) the volume of gas has expanded 20/273,15=0.0732 roughly 7%.

In your case filling the gun indoors at 20 degrees and the leaving it outside to cook in the sun for a while so the black tube reaches 80 degrees is bad! At this temperature you will have 3660 psi in the tube.

Its good to be aware of this, especially if you leave the gun fully charged in a car on a hot day...

For CO2 its totaly diffrent - you can shoot with CO2 at low temperatures... well you could but it sucks