Whether you’re out skiing, you’re stranded in a broken-down car or you’re begging the kids to come in from their hours-long igloo-building project, it’s important to face some hard cold facts: Very cold temperatures can be dangerous — even deadly.

Each year some 1,300 people in the United States die from hypothermia, according to the Centers for Disease Control and Prevention. Elderly people, homeless people, very small children and people with certain medical conditions are most at risk. But hypothermia — and frostbite — can strike anyone who’s unprepared to be out in the cold, or whose judgment is impaired because of factors like dehydration, fatigue or intoxication, says Paul S. Auerbach, MD, chief of emergency medicine at Stanford University School of Medicine and author of “Wilderness Medicine.”

Here’s what you need to know about the two most serious conditions caused by exposure to extreme cold so you can protect yourself and your loved ones.

Hypothermia

When you’re cold, you shiver. All that teeth-chattering is designed to generate heat. It helps, but eventually the body will begin to lose more heat than it can create. Hypothermia occurs when body temperature dips to 95 degrees F or lower. (Normal body temperature ranges from 97.8 to 99 degrees F.) This can happen even when the ambient temperature is above freezing, especially if a person’s skin or clothing is wet, says Douglas G. Sward, MD, professor of emergency medicine at the University of Maryland School of Medicine.

What it looks like: Intense shivering is an early sign. Others include fatigue, confusion, slurred speech, lack of coordination and drowsiness. As hypothermia progresses, the body stops shivering, muscles become rigid, and pulse and breathing slow. A person with severe hypothermia may eventually lose consciousness. His skin may appear blue-ish and feel ice-cold.

What to do:

  • If you suspect someone has hypothermia, call for medical help.
  • While you’re waiting for help to arrive, if his clothes are wet, replace them with dry ones.
  • If you’re outside, try to get him out of the wind.
  • Place a sleeping bag or blanket underneath him as insulation from the cold ground.
  • Cover his head.
  • Apply warm compresses (never direct heat) to the center of his body — chest, neck and groin.
  • If he’s alert and isn’t vomiting, offer him a warm, sugary beverage. Do not give him alcohol or a drink that’s highly caffeinated.
  • If he stops breathing, begin CPR.

Frostbite

The body also reacts to extreme cold by restricting blood flow to the extremities in an effort to conserve heat. This can lead to frostbite. The first stage, sometimes called “frostnip,” is easy to treat. But as frostbite progresses, ice crystals form inside and outside of cells, explains Sward. Deep frostbite extends beyond the skin. It can affect fatty tissue, muscle and even bone. Frostbite is most common in fingers, toes, chin, nose, cheeks and ears. The damage can be so severe that the tissue in affected body parts can die and require amputation.

What it looks like: The first sign is tingling or numbness, usually in the fingers, toes, ears or face. The skin in these areas will turn pale or red and feel cold to the touch. As frostbite progresses, skin will turn white, waxy or grayish-yellow. Frostbitten body parts may start to swell and become solid. If joints are affected, they may become too stiff to move easily.

What to do:

  • If you or someone you’re with experiences pain or loss of feeling in any body part, get yourself of them out of the cold right away.
  • If frostbite has already occurred, remove jewelry or tight clothing.
  • Do not rub or massage the skin.
  • While waiting for medical attention or on the way to the ER, keep affected areas dry and loosely covered.
  • Unless it’s absolutely necessary, a person whose feet are frostbitten shouldn’t walk. “This is critical to prevent thawing and refreezing of frostbitten tissue, which can lead to severe tissue loss that is much worse than the initial injury,” says Sward.

Practice prevention

The biggest mistake people make when venturing into the cold is not dressing appropriately, says Auerbach. Wear several layers of loose-fitting, lightweight but warm clothing. Start with a layer of moisture-wicking fabric such as polypropylene. Do not wear cotton against your skin; when it gets wet it stays wet. Add warm tops and bottoms. Top it all off with a coat or jacket made of a tightly woven, water- and wind-resistant material. Cover your head, neck and face with a hat and scarf or a balaclava. Protect your feet with warm socks and weather-resistant shoes or boots. For hands, mittens are warmer than gloves.

Common sense is just as critical as dressing warmly, adds Sward. That means keeping well-hydrated and well-nourished and not drinking alcohol. It also means staying indoors unless you absolutely have to be outside when the wind chill hits negative numbers.