I live in Tucson, AZ, so I know what you mean about heat! I'm using monoblock Atma-sphere M-60 Mk 2.2's, with 16- 6AS7 triodes running in class A bias! And I also listen nearfield, which means that the amps are about 10 feet away from me.
Daytimes, I run my A/C. But for serious listening at night, I shut off the A/C. I can listen for about 1 to 2 hours at a time, and then I have to run the A/C for about 15 minutes to cool things off. Then, back to the music.
One of the nice things about the desert is that the ultra low humidity makes it feel cooler than it really is; the heat index is LOWER than the actual temp. [Right now, 11:30 AM, the temp is 88, but the heat index is 82.] And the amps make dandy space heaters in the winter, as outlying areas of Tucson can drop into the mid 20's at night [we're at 2500 to 3000+ feet of elevation].
Temps in Arizona can vary wildly depending upon elevation. Flagstaff [6000 feet] has snow and cold temps in the winter. Northern AZ is pretty much high elevation with REALLY low population. Phoenix regularly hits 112 to 117 in the summer, Lake Havasu, Bullhead City, and Yuma can top 120 in the summer, but Tucson ranges from 102 to 108 in the summer, and rarely tops 110. Hey, I can handle this heat much better than the mid 90's in Miami [used to live there] with it's 90+ humidity and stronger subtropical sun [lower latitude than Tucson].