If he has been drinking more water because of the higher temps... I would say it is normal. Im in Fl and our Index has been 110-120 the last few weeks. And my horses are drinking alot more than normal. And as a result peeing more. If you havent noticed a difference in water intake you may want to ask your vet.
Many people have sighed for the 'good old days' and regretted the 'passing of the horse,' but today, when only those who like horses own them, it is a far better time for horses. ~C.W. Anderson