The baggage hold used for transport of the animal is conditioned to an average temperature of 20° C.
It is not possible that your pet can travel on all aircraft types, because some of them does not have heated baggage hold but simply ventilated to a temperature of 5° C, which is not acceptable for your pet comfort. Obviously the holds are pressurized.
Moreover, it is not possible to transport your animals at certain times of the year because airports can't ensure quick recovery of the animal on the arrival of the flight.
Indeed, outside temperatures imply an immediate recovery of the animal so that it does not remain on the tarmac before being transferred to its destination.