How does temperature affect CO2 performance?

CO2 pressure is set by temperature, not by how full the cartridge is, so cold weather drops pressure and hot weather raises it.

On a cold winter day a CO2 pistol might give 30 shots before pressure falls too low to cycle, while the same gun on a warm summer day delivers 60 shots and higher velocity. Rapid shooting also chills the gun as liquid CO2 vaporizes, so velocity sags within a string. Below about 50 degrees F, CO2 guns become unreliable.