Rickair7777 hit that nail square on the head. If your nephew is going to RAA in Mesa, he's at William-Gateway Airport. The only other school I know of out there is AllATPs. From what I hear, they're pretty decent. But tell him to definately avoid the academy route.
If he's willing to relocate, there's a whole bunch of FBOs outside of the Phoenix area that provide friendlier conditions. I remember at RAA there were days when no planes could be dispatched because the temp was way tooooo high. It's not conducive to train in an unpleasant enviroment. Might as well go somwhere where you will be able to fly daily, and not be grounded due to weather.
... and then there were the Monsoons.....
I'm pretty sure you've experienced them!!