I think you will find there is significant variation in procedures between airlines and operating environments.
On the ground we tend to see higher cargo compartment temperatures if it is hot outside, particularly if the APU is shutdown for a turn around. Ground air does not tend to be very effective for cooling the cabin let alone the cargo areas. Once the cargo doors are closed and engines (or at least APU) running, then temperatures become more manageable. Once at altitude, then warming becomes more of an issue. Crews will monitor temperature and adjust accordingly. Some aircraft have a humidifier for the flight deck, but I'm not aware of any with one fitted for cargo bays nor any humidity indicators.
Typical cargo temperature settings are around 18-21 deg C when livestock is carried.
. . . and still doing smallies locums between trips.