The reasons why puppies stick out their tongues in summer:

1. Dogs do not have sweat glands, and their main way of perspiration and heat dissipation is by sticking out their tongues.

2. Dogs will also expose their tongues when sleeping. It may be caused by the dog dreaming.

3. It may also be the expression of a dog acting coquettishly towards its owner. Sticking out its tongue is also their skill.

4. If you find that your dog keeps sticking out its tongue and panting, it may be caused by illness.

5. Dogs will also stick out their tongues to relieve themselves after strenuous exercise.

6. Some dogs are born with tongue protrusion syndrome, which causes them to always stick out their tongues.