Does my dog need a winter Dog Coat or Sweater?
Does your dog "need" dog clothes? Maybe and maybe not. Clothes serve a function other than being cute. Some smaller and older dogs can't regulate their heat thermostat in cold weather,have short thin hair or are kept clipped short to prevent matting. These dogs might need a coat, sweater or jacket depending on how cold your winters are and how long they take to go potty.
Sure, dogs come equipped with their own external layering system, but some dogs have lighter layers of fur than others, and some are not genetically suited to the environments in which they find themselves transplanted. So your dog may in fact be extremely uncomfortable with the winter temperatures — as uncomfortable as you would be if you went outside without clothing.
Of course, short, thin hair is not the only prerequisite for outer clothing. Dogs that tend to have short-cropped hair — like poodles, which may grow thick hair but which owners tend to keep short to avoid matting — should also be given a sweater to protect them from very low temperatures. Also, older dogs with weaker immune systems and dogs with diseases that impair hair growth (i.e., Cushing’s disease, hypothyroidism) typically need an extra source for warmth, and this can be easily provided by a sweater or jacket, even indoors.
Conversely, larger dogs with dense hair coats do not have a need for additional insulation, and would be very uncomfortable if they were forced to wear outer clothing, possibly to the point of physically overheating. Their fur is already genetically designed to protect them from extreme winter temperatures. The Siberian Husky, Malamute, Akita and Saint Bernard breeds are all excellent examples of dogs that are perfectly suited to cold temperatures, while the Chihuahua, Greyhound, and many terrier and pinscher breeds are good examples of dogs that would do well with a little extra outer insulation.