Excessive exposure to the cold bite of winter can lead to frostbite and hypothermia, an even more serious condition. Frostbite is limb-threatening; hypothermia is life-threatening.

Frostbite happens only in subfreezing temperatures and usually affects the fingers, toes, heels, hands, nose, and feet. Superficial frostbite is characterized by numb, red, and slightly swollen skin that becomes red and flaky after thawing. With deep frostbite, blisters appear and the skin may become cold, waxy, pale, and hard. Pain may lessen and disappear.

Hypothermia is even more dangerous, impairing motor skills, speech, and decision-making abilities. As hypothermia progresses, victims may seem confused and weak, may behave irrationally, and may even deny feeling cold. As the body chills, muscles become stiff and the heartbeat uneven. Unconsciousness and death may follow. Hypothermia doesn't require subfreezing temperatures. People who get caught in rainstorms, fall into water for an extended period, or perspire in cool weather can become victims.

The National Safety Council offers these tips for protecting yourself from the cold:

• When outdoors, dress in layers. A good choice for the layer closest to your body is polypropylene or polyester, followed by wool or fleece, then a water- and wind-repellant material. Choose wool or polyester mittens rather than gloves, and wear a hat.
• Eat and drink often (but avoid caffeine and alcohol). Food produces heat for the body and fluid increases blood volume, which protects extremities.
• If you think you have frostbite, immerse the frostbitten parts in water that is not quite hot to the touch. Take aspirin for pain and seek medical attention.
• Victims of hypothermia should have wet clothing removed and should be covered completely. Don't place the victim near a heat source to stop shivering, because shivering is the body's way of producing heat. Seek medical attention immediately.
• When traveling by car (or hiking) in cold climates, pack food high in carbohydrates and sugar, waterproof matches, a container to melt snow for drinking, wool clothing and blankets, a shovel, and a flashlight.

If you are stranded and far from help, limit physical activity to preserve heat. Remain in your vehicle and periodically run the engine. Don't touch metal surfaces and keep your hands in your groin or armpits. If your fingers become numb, perform reverse windmills with your arms to recirculate blood. Huddle with others, or curl up in a ball if you're alone.