We would keep our dog in our motorhome for a few hours if we were at a campsite with AC running. If we stopped for lunch and it was hot we would run the generator to keep our dog cool. Of course there is always the chance that the generator or AC would fail, but an RV is not the same as a car. In hot sun a car will reach dangerously high temperatures in just a few minutes. With shades drawn, an RV will take much longer to heat up, and even then won't get much hotter than the outside ambient temp if all the windows are covered.
