Well, I've run GPS under the hot sun (while being docked in car) and the phone became pretty darn hot. It worked perfect though.
I don't think cracking due to heating should be a problem. It all depends on what kind of glass they used as well.
Anyways.. I got married in Karachi in a June and had to be on drips for the first time of my life due to dehydration.. so I can feel you!
Well, Pakistan has extreme temperatures, right from cold to hot.