How warm your dog is able to physically keep himself may depend on his breed, size and even age, but if he just doesn’t have a heavy hair coat, there is only so much curling up he can do to save heat. Smaller, light bodied breeds, toy breeds, and breeds that naturally have very short or thin hair coats benefit from a warm dog sweater for when they need to go outside, or for just hanging around the house. A sweater can make a significant difference in your dog’s feeling of well-being.