In extremely warm temperatures, you must look for signs of heat exhaustion in your dog. They don't sweat. They dissipate their excess body heat by evaporation through the tongue, mouth and nose. They pant to cool themselves and they speed up this process by speeding up their panting. Dogs overheat more easily than their human counterparts. Older dogs are in more danger of heat exhaustion just as older humans are more unserviceable.
Signs to look for include heavy panting, deep labored breathing, increased salivation leading into dry gums, a discoloration of the gums, thick stringy saliva, signs of weakness, confusion, and vomiting. If not noticed and treated or a change to alleviate these conditions can lead to heat prostration or heat stroke.
If you see any signs of heat exhaustion, immediately take him out of the hot sun, make sure he has plenty of water available. You can try cooling his paws and head by dousing him with water to bring down his temperature. It is best to use cool or tepid water rather than really cold water. Ice packs can be applied to armpits, inguinal region, or neck. Directing a fan on him as you apply the water and ice packs can be helpful.
Steps to avoid heat exhaustion in your dog:
Brush your pet's coat. Shaving their coat can leave their bare skin exposes them to possible sunburn. Dogs and cats, especially ones that have light colored coats, can sunburn and it's possible for your pet to get skin cancer from overexposure. If you want to play it safe, use a pet safe sunscreen on your dog's lip area, inside the dog's nostrils, on the tip of the nose and inside the ears if they stand up.