On very hot day, why does a dog extend its tongue out?

Unlike humans, dogs do not have sweat glands, therefore they cannot excrete water to cool down their skin. Instead, dogs rely on the evaporation of their saliva to cool their skin down. They hang their tongues out so the saliva can evaporate and move over their skin and fur. read more

On hot day a dog extend its tongue because it’s hair prevent the sweating, so the dog must lower its corporeal temperature with the breathing. read more

Normal temperature for dog is between 100.5-102.5. If he has over 103, I'd definitely have him see the vet today. Make sure he's drinking sufficiently, as diarrhea will cause him to lose more fluid during a b.m. and if he does have a low-grade or higher fever, this too, will cause him to become more dehydrated. read more