I have a dog with a double coat. They require a lot of maintenance — brushing, brushing, brushing — and a vacuum cleaner that can handle mountains of shed fur on your floors. The thick coats always beg the question, especially as summer approaches, of how one can possibly keep these dogs cool. 
I’m often asked if I get my dog shaved for the summer and the answer is, no. I was told not to bother by her previous owner and by my vet. People not in the know about double-coated dogs may consider that answer cruel or neglectful. The opposite is true, and here’s why.
A double coat consists of a short, crimped undercoat and longer guard hairs. The undercoat is highly efficient at trapping air and insulating the animal. It keeps them warm in the winter and cool in the summer. The undercoat sheds in spring and fall and helps regulate temperature. And this is where the brushing comes in. Keeping up with brushing maintains the health of the undercoat and removes excess fur, keeping the dog cooler in hot weather. Make sure that you use the proper kind of brush for gently removing this fur — a rake-style brush works well, but check with a trained groomer or your vet about what they recommend.
Guard hairs are harder in texture, thicker in diameter, and longer than the downy undercoat. Considered the dog’s primary coat, the guard hairs protect the skin from superficial injuries. Guard hairs also provide protection against the sun’s UV rays and actually insulate the dog from the heat. If they are shaved off, that protection is gone. Not only will sunburn be painful to your dog, it can take a long time to heal as well. The dog may have scaling and dandruff for quite some time, even after the hair has re-grown. To compound the problem, guard hairs do not grow back to their original condition, causing tangles, matting and increased vulnerability to temperature.
Common dog breads that have undercoats include German shepherds, Pomeranians, Chows, Huskies, Malamutes, Samoyeds, Golden Retrievers, Bernese mountain dogs and my less common Yugoslavian shepherd. If you’re not sure, check with your vet. Dogs like poodles, Maltese, Shih Tzu’s, and other dogs, which do not have undercoat and whose hair grows continuously, can be shaved regularly.
Unless your double-coated dog has passed the point of no return in the matting department, the best type of grooming for these dogs is vigorous undercoat raking. Owners can consider shaving a strip on their dog’s belly during the warmer months, so that they can lay on cool surfaces, and get maximum coolness with a special tool that helps remove the undercoat, but leave the rest of the fur intact. If mats are your main concern, then it’s best to simply keep up with them so they don’t get to the point of having to shave your dog.