Wind Chill, Hypothermia & Frostbite

Wind chill, hypothermia, frostbite, blizzard

In the next few days, a "polar vortex" will push Central US and Ohio Valley temperatures below zero, with wind chills around -40 degrees.

To avoid frostbite and hypothermia, it's important to understand how a human body reacts to extreme low temperatures.

The human body loses heat through convection, evaporation, conduction, and radiation. The rate of surface heat loss through convection depends on the wind speed across the skin. As skin heats the air around it, an insulating boundary layer of warm air forms against the skin. Moving air disrupts the boundary layer, allowing for new, cooler air to replace the warm air against the skin. The faster the wind speed, the more readily the skin cools and chills.

A person wearing wet clothes, will lose heat quickly because the wet cloth will conduct heat away from the body more rapidly, and the evaporating moisture carries away heat.

At or below 0 °C (32 °F), blood vessels close to the skin start to constrict, and blood is shunted away from the extremities via the action of glomus bodies. The same response may also be a result of exposure to high winds. This constriction helps to preserve core body temperature. In extreme cold, or when the body is exposed to cold for long periods, this protective strategy can reduce blood flow in some areas of the body to dangerously low levels. This lack of blood leads to the eventual freezing and death of skin tissue in the affected areas. There are four degrees of frostbite. Each of these degrees has varying degrees of pain.

The Wind Chill is the temperature your body feels when the air temperature is combined with the wind speed. It is based on the rate of heat loss from exposed skin caused by the effects of wind and cold. As the speed of the wind increases, it can carry heat away from your body much more quickly, causing skin temperature to drop. The Wind Chill chart below shows the difference between actual air temperature and perceived temperature, and amount of time until frostbite occurs.

What is Frostbite?
Frostbite is an injury to the body caused by freezing body tissue. The most susceptible parts of the body are the extremities such as fingers, toes, ear lobes, or the tip of the nose. Symptoms include a loss of feeling in the extremity and a white or pale appearance. Medical attention is needed immediately for frostbite. The area should be slowly re-warmed.

What is Hypothermia?
Hypothermia is abnormally low body temperature (below 95##F). Warning signs include uncontrollable shivering, memory loss, disorientation, incoherence, slurred speech, drowsiness, and apparent exhaustion. Medical attention is needed immediately. If it is not available, begin warming the body slowly.

How should I dress during cold weather?

Wear layers of loose-fitting, lightweight, warm clothing. Trapped air between the layers will insulate you. Outer garments should be tightly woven, water repellent, and hooded.
Wear a hat, because 40 percent of your body heat can be lost from your head.
Cover your mouth to protect your lungs from extreme cold.
Mittens, snug at the wrist, are better than gloves.
Try to stay dry and out of the wind.

Also keep in mind that pets are just as susceptible to frostbite and hypothermia as humans are. If it's too cold for you, it's too cold for your pet.

Wind chill, hypothermia, frostbite, blizzard, wind chill chart