Dogs have two ways to cool down when they overheat. One method they use is panting. While panting cools dogs, it also causes them to dehydrate faster from losing moisture through their tongues. They need access to clean, cool water at all times. Another method a dog uses to cool down is to lie down somewhere cool, as dogs cool from the bottom up. They lie on their bellies in a cool spot, cooling the body quickly.
Dogs and Hyperthermia
Most people have heard of hypothermia, where the body gets too cold, but the lesser known alter ego is hyperthermia, where the body gets too hot. A dog's normal body temperature is around 100 degrees Fahrenheit. When temperatures reach around 106 degrees, a dog's body becomes unable to cool him through panting, and he will suffer heatstroke. This is why a dog should never be left in a closed car for even just a few minutes.
Losing Heat Through the Paws
Dogs don't just pant to reduce their body temperatures, they also lose heat through the pads of their paws. This is why dogs like to find a cool place to stand or to lie when it's very hot. The pores of the skin on the paw pads allow moisture to escape and cool the animal. He will lie or stand on cool floor tiles or on a cement floor in a basement until he cools down adequately.
Brachycephalic Dogs and Heat
Short-faced dogs such as bulldogs have more trouble staying cool than dogs with longer faces. They cannot pant themselves cool as easily, so they need extra help. Giving those dogs a cool place to lie helps keep the animals' body temperatures regulated. Giving them fresh water frequently helps to keep them hydrated and cool. Hot water is no good; cool water is great. But icy water is a bad idea, as it constricts blood vessels and restricts the flow of blood.
Dogs Don't Use Common Sense
While a cat knows enough to slow down or stop to rest when he gets too hot, a dog doesn't. He will play until he collapses from heat exhaustion. You need to be responsible about the dog's playtime when temperatures rise. Frequent rest breaks in a shady place, with accompanying water breaks, is the best way to rest and rehydrate the dog's body so he can get up and play again without dangerous consequences.