That's actually.. quite smart.
When I'm thinking of good places to plant a mining farm I've always focused on low temperature countries and countries with low electricity cost. The desert would be the last thing I would've think of. That's an interesting idea, though I don't know how you're going to setup a cooling system for temperatures THAT high.
Shade and fans for airflow. Operating temperature for a GPU is quite high, you need to put enough
cooler air across them to keep them in range. Even if the air is 40deg C, if you blow enough it'll keep at 60-70deg. Just need an a lot of fan power. Maybe its not that simple, but i can see how some clever engineering could make desert mining viable to take advantage of the abundant daytime power... however batteries for sustained overnight running is the bigger issue imo.
I don't think any miners could operate at 60-70 c degree.