Make a Paddle Pool
Nothing cools a dog off quite as well as hanging out in some cold water. If you’re outside, let him waddle around in a nearby lake. If you’ve got a house with a backyard, you might want to invest in a little wading pool where he can literally and figuratively chill. At home, you can fill up the bathtub with some cold water and kill two birds with one stone by giving him a bath as well. At minimum, there’s also the option of taking a cold, wet towel and pressing it to his neck, under his armpits, and between his hind legs.