Some people believe that long fur insulates a dog and keeps them cool. After just minutes the coat begins to hold in body heat. Long-haired dogs in warmer climates should be trimmed short. Even with air conditioning, these dogs can get ridiculously hot.
If you like running or hiking with your dog, you should keep the dog very short and stop for rest and both drink. If you are feeling hot, your dog probably is also, so pour some water on their chest. The best places to cool a dog down are on the neck, pads of the feet, and belly.
Smushed-faced dogs, such as bulldogs, should not exercise or be left out in hot weather without the permission of a veterinarian. These dogs often have small tracheas and long soft palates, which decrease their ability to cool themselves. You can also ask your vet about surgeries that can shorten the soft palate and increase the ability to exercise.
Dogs left in the yard need shade and preferably a small wading pool filled with cool wate, dog houses can become very hot. Finally, whether it is hot or cold, every dog should always have an adequate supply of fresh drinking water.