If he's drinking more, which as you say may be due to the hot weather, he'll need to pee more. If he's cocking his leg less then you'll probably notice him doing longer pees when he squats because those are the times when he's peeing because he needs to, as opposed to doing lots of short pees when marking.
William was castrated at 15 months because of an undescended testicle. He cocks his leg now and then but mainly waits until he needs to pee then squats and pees a lake! If Humphrey is doing that you may notice his urine looks quite yellow and smells a bit strong, which can happen when they hold on for some time.
But if you're concerned, take Humphrey and a pee sample to the vet, who will do a dipstick test there and then.
