Any temperature less than our normal core temperature of 98.6 can contribute to to hypothermia. The colder the temperature, the greater the chance of hypothermia setting in. While cotton is great for warm weather, it can be quite dangerous in cold temperatures. It absorbs moisture and holds on to it, helping to transfer the warmth away from your body. Wear clothing made from synthetic fibers that are hydrophobic, such as polyester or polypropelene.
Most body heat is lost through the head.
Drinking alcohol can be quite dangerous, however. Alcohol increases the surface blood flow by dilating the capillaries. This gives a false sense of warmth because the skin feels warm. Avoid alcohol, coffee, tea, and tobacco because they all expand the capillaries, causing your body to lose heat. Give them warm sugar water - no solid food Add heat directly to the body using something such as a hot water bottle, heat packs, or warm rocks.