So does tobacco. A thermos of hot cider or other sweet drink will be better for you. Once any part of you gets cold, warming it is very hard without an external heat source. So as soon as something begins to feel chilled, run in place for a while or do some jumping jacks. You produce several times more heat during mild exercise than at rest, and good circulation will carry this heat all the way to your toes and fingertips.
Women produce less heat on average than men.
People with good muscle tone generate more, even at rest. Vigorous exercise raises anyone's metabolism for up to six hours afterward, so late afternoon or early evening would be a good time for a workout. Beware of exhaustion, however, which leaves you prone to rapid chilling. A little-known cause of chills, headaches, and ill feeling in winter is dehydration. When the body runs low on water it conserves fluid by reducing circulation to the extremities, which means your hands and feet freeze quicker.