considering my dane has a single coat of fur, you can see her skin, and she shivers and shakes when it is cold, she gets a coat. When she comes inside with bloody feet, and cracked paws, cuts inbetween her toes, she get boots. It doesn't matter if it is cold out or not. Most of her issues come in the summer. If she didn't tremble, her nose that is usually pink is white due to cold, and her pink pads are white, she is cold and needs the jacket. so instead of her going out and freezing.....s he gets a jacket and boots. and when it is -10....they don't go out for more than 2 minutes....and YES they still have a jacket on...if not they harass me to get warm.