Our biggest problem in high temps has not been keeping the RV cool but LOW VOLTAGE in the campground.
Have had to run the generator more than once during the hottest part of the day because the voltage of the shore power in the park or campground was to low.
Have a 27 foot with a 13,500 and have stayed cool in temps as high as 115
Tips
Run the generator and roof AC while driving so that the RV is not hot when you stop.
Use a outside cab wrap to cover the cab windows and windshield
Close off the cab area from the motorhome we use a blanket.
Close off the overhead bunk.
During the hottest part of the day close any areas not being used such as bedroom or bathroom. A warm bathroom for a few minutes will not kill anyone.
Park with the passenger side to get the afternoon sun and then put the awning out
Vent coversWindow awning are great but since we do not have them we have a
shade cloth cut just bigger than the dinette window and use six Velcro tabs to attach it pn the outside
Do not use the oven or cooktop heat meals up in the microwave.