Few years ago we camped around Zion and temps were 105, and down around Kanab they were approaching 118. Driving we had the dash AC, generator along with both house ACs on full blast - it was still warm.
While parked I used our awning screen to hang over the main slide out. During the heat of the day we brought in the main slide to reduce the volume of air the AC units had to cool. While parked the dual ACs did just fine keeping the RV cool. The key was to keep it cool all day, once it's hot it's difficult to recover from the heat.
