When temperatures go into the 100F's, they put up  signs at Canyonlands National Park trailheads to warn that you will literally die (!) if you try to hike during the heat of the day.   They are not exaggerating, either.   Even though it is actually possible to hike in the early, early morning or by moonlight, no matter how many electrolytes you drink, you still need shade to hunker down during the afternoon. 

 Frankly, when it gets super hot the best plan is, consider doing the hike in a different season when the weather is not an existential threat.    Last year I went on a  desert backpacking trip where  it was so hot we decided to  change our route on the fly from a planned loop hike in order to do an out-and-back in  a canyon with more reliable water.    It can be hard to let go of plans, but even in retrospect I  think it was a truly excellent group decision to be safe instead of trying to tough it out in the heat.