I have been thinking about all the concern for pets. We do leave a vent open and the fan on with the thermostat set in the mid to high 80s.
That said, I propose a test for those that are concerned with the temperature inside you RV. I have done it as I was concerned with cold temperatures but this summer I have had the thermometer in the water bay and another on in the kitchen counter. These are cheap Radio Shack ones that record highest and lowest temperature seen since reset. Typically my MH internal temperature on the kitchen counter lags the outside temperature by 6? to 10? F. the other day and again today our outside temperature was in the mid to high 90s. The MH only got to 83? before the outside temperature started down. Right now the out side temp is 77? and the MH counter is at 79?. The gap will widen as the outside temperature goes down till the difference is in that 6? to 10? range.
This is with the MH all closed up, no cushions in the vents, vents, closed, DayNight shades down and the front windshield covered by the internal drapes. There is no shade in my Driveway, the awnings are stowed and there are no outside window coverings.
Once you know the way your RV heats and cools, you may rest a little easier when thinking about your pet in an RV.
One real hard rule, there must be adequate water for your pet. In our case a pint is sufficient for the cat for a day, even on a hot one.. Our neighbor has a Great Pyrenees and I think that dog uses at least a gallon in 8 hours in this weather.