In hot weather, if we stop enroute at a grocery store, we let the generator running with the a/c going.
When at a CG, if we leave the dog, we have the a/c running, close the curtains, and set up battery operated fans as backup, in case of power failure. We never leave them very long when it's hot out, and leave our phone numbers at the office in case of a problem.
I also have a cooling mat for the dog to lay on.
The interior of any vehicle or RV can heat up very quickly on a hot day and turn to disaster.
No way I would leave a dog in an RV for several hours without being hooked up to elec and having the a/c running. Even with the genny running and a/c on, I would not leave them for hours, as something could happen and the gen could shut off.