There’s an old saying, “If your feet are cold, put on a hat”. You could have the nicest coat ever made, but nothing will warm a particular body part more than the body parts next to it. There’s tons of blood flowing close to the surface on the head, neck, and wrists; having those areas exposed turns your skin into a blood-cooling radiator. So consistent, thorough coverage and tucking in layers will make your winter clothes warmer than the sum of their parts