Double coated dogs refer to the animals that, like Huskies, have two layers of fur. The first, or undercoat, are the fine, fluffy hairs that are short and crimp (closest to the skin). It's the fur that sheds; light and soft. This layer is excellent at trapping air and insulating the dog. Essentially it keeps them warm in the winter, and cool in the summer.
The topcoat is made up of tougher guard hairs that don’t shed, and protect your pet from the sun’s harmful rays and bug bites. It actually insulates them from the heat. What this means is: do not shave your double coated dog. It’s a mistake to think you’re helping your animal stay cool, particularly in summer, when evolution has provided them exactly what they need to survive. By stripping them of their natural ability to heat and cool themselves, you could be doing more harm than good.
A key piece of understanding in this matter is that, unlike humans; dogs do not cool themselves through their skin. At most, it is only the pads of their paws that sweat. Their main mode of cooling comes from panting.
Some other common reasons folks shave their doubled coated dogs are the thinking that the animal will stop shedding. Pooches with undercoats shed, no two ways about it. But even after a shave, while the hair may be shorter, it can still shed.
Another is, "it'll always grow back". Sometimes it will, other times it won't. The older the pooch is, the less likely it is that the topcoat of guard hairs will grow back. This leaves them with the undercoat, giving them a patchy, scruffy look. It can alter their coat for the rest of the dog's life. Not only does it look bad, but you can end up having to shave the hair continuously from then on and once again, you strip them of their natural ability to protect themselves.
In conclusion, when you shave a double coated dog, you may irreparably impair their ability to properly heat/cool themselves and protect their skin. The best way to keep this kind of dog cool and comfortable is to regularly bathe and brush them. The only reason a person might need to shave their double coated dog is if the hair is so matted, it's the only option.
Seattle Dog Health Examiner