Dogs and cats must rely on panting to lower their body temperature during physical activity or hot weather. You should not rely on the dog to realize he needs to take a break from playing because the excitement of being out and about may cause them to ignore the need to take it easy. High humidity levels cause panting to be less effective and increase the risk of heat exhaustion and heat stroke. The difference between these two conditions is the severity.
The symptoms of heat exhaustion include extremely heavy panting, weakness, disorientation, and possibly vomiting. Dogs experiencing heat exhaustion are usually panting so heavily that they will not stop even for a second to swallow.
A warning sign that a dog with heat exhaustion is progressing to heat stroke is diarrhea. Diarrhea may be followed by seizures or loss of consciousness (coma). Animals with these severe signs often do not survive. Any animal suspected to have symptoms of heat exhaustion or heat stroke should be seen by a veterinarian immediately.
If your dog is showing early signs of heat exhaustion, immediately stop any activity and move them to an air conditioned environment if possible, or at least to a shaded area. Offer cool water, and if available, ice packs can be placed on thin-haired areas like the abdomen and armpits. If your pet is disoriented or showing any symptoms beyond panting that resolves within a few minutes, she should be seen by a veterinarian immediately, as some heat-related complications may take several hours to develop.