90 degrees and humid, so we started out with a hack in the occasional shade of the training track. We worked on letting go in his poll. Then out for a hack in which, to my surprise, he did quite well despite the heat. In fact, in the first canter, he got a little rowdy! In the second canter we were able to actually stay a bit softer and on the aids.
By the time we hacked home from the marathon course he was fairly light in the bridle. I grazed him for a few minutes before turning him out.