Mountain Biking in the Heat....Meh.

So it is hot out there; 90+ degrees with a 100% chance of sweat!  What are you going to do about it?  Sit in your air-conditioned home and complain about it (maybe watch Jerry Springer or Court tv) or are you going to go out and ride?  You already know my vote.  After all, I have always felt it is fine to ride in the heat as long as I don't over do it.  I found a decent article about just this topic.  Still, last weekend, after a 55 mile ride (that started at 7am, in order to miss the most intense heat) I had a headache for the remainder of the day. Could the heat have caused the headache?  Maybe grinding my teeth during the ride?  Maybe from the beer I chugged immediately after the ride?  Or maybe (my vote) it was not the heat (or teeth, or beer) but the lack of sunglasses.  I recall reading somewhere that being in the sun, squinting all day, can lead to headaches.  Another big ride the weekend (60+ miles), so maybe I try wearing some shades (and maybe some preemptive Advil) to see if I can fend off headaches.  If it doesn't work, I will try switching brands of beer (and drinking more of it).