What about this heat.

Emerson Nagziger offers his opinion of the effect of heat on our crops.  One thing to keep in mind is that crops that have adequate nutrition will hold out in the heat longer than those that have a deficiency.  Nitrogen is very important to drought and heat resistance.  Compaction can contribute to drought problems.  One of the reasons that early planted corn will continue to perform is that it was planted with minimal compaction.  Stands of early planted corn may not be perfect, but other advantages are going to allow them to outperform later planted corn as usual.