Depends on the aircraft type, but nothing gets unreasonably cold.
Contrary to some belief, all the holds are pressurised.
Most aircraft have one of the holds heated, ducted with the passenger cabin. This is the one that live animals are carried in, and anything else that needs the temperature. Whether your baggage is also in there is a chance, hence the different experiences.
The remaining holds are not heated, saves fuel. Their temperature depends on how many containers are in there and, of course, the flight duration. If it's filled, the temperature does stay reasonably close to what it was at departure, only dropping a degree or two per hour. If only part filled, it tends to drop a bit quicker. But nothing too untoward. bags are (sometimes
) delivered in less than an hour from the aircraft being at altitude, they do not come out frozen stiff, nor do the contents. Water bottles in bags do not freeze and burst. Broken bottles, due to rough baggage handling or bags rolling in turbulence inside a container only part filled are of course something else.
For bulk loaded bags (not at Heathrow T5 where it is all containerised) bags delivered wet, hot, etc are generally because they have been left outside after unloading.