I did 86 miles this morning, with a max recorded temp of 115. Every time I stopped to refill my bottles, I removed my helmet and soaked my hair with cold water, also putting some down my back. Did some of that while riding too, and especially if stopped at an intersection. Boosted the evaporative cooling a bit I have a Trek "Circuit" helmet, which lists for $99. Pretty cool, and they have free crash replacement for a year.

So to answer your question - probably not.