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Understanding the dangers of wind chill




Wind chill is the term used to describe the rate of heat loss on the human body resulting from the combined effect of low temperature and wind. As winds increase, heat is carried away from the body at a faster rate, driving down both the skin temperature and eventually the internal body temperature. The wind chill index combines the temperature and wind speed to let you know how cold the wind “feels” against your skin. While exposure to low wind chills can be life threatening to both humans and animals alike, the only impact that wind chill has on inanimate objects, such as vehicles, is it shortens the time it takes the object to cool to the actual air temperature. (It cannot cool the object down below that temperature.)

The National Weather Service office in Jackson will issue advisories or warnings whenever the combined effects of temperature and wind will create a threat. Wind chill advisories will be issued whenever the sustained wind speed will exceed 10 miles per hour creating wind chill equivalent temperatures of 10 to 24 degrees below zero. Wind chill warnings will be issued if the sustained wind speed will exceed 10 mph and the wind chill equivalent temperatures are from 25 degrees below zero and lower. Sustained wind speeds less than 10 mph do not create a significant difference from the actual air temperature. Exposed skin will freeze in 30 minutes within the advisory temperature range, and in 10 minutes when the warning criteria is reached.

To understand the dangers and warning signs associated with the cold, it is important to understand how the human body regulates its temperature. The human body loses heat during the winter because of the conduction and convection of heat from the skin to nearby air, due to evaporation of moisture from the skin surface, and due to normal respiration. To compensate for this heat loss, the body burns energy to produce heat to keep the body temperature at a relatively constant level. If, however, a body loses heat faster than it can produce heat, the body temperature will cool to below normal levels, a medical condition known as hypothermia.

Hypothermia will gradually worsen unless the overall rate of heat loss can be stopped. The warning signs for hypothermia may start with shivering and shaking and may end in death. Initially, as the body temperature starts to drop, shivering begins. At the same time, the brain begins to reduce the amount of blood circulated to the extremities of the body to conserve heat for the vital organs near the body’s central core. If the central core of the body continues to cool, uncontrollable shaking, memory loss, disorientation, incoherence, slurred speech, drowsiness, and apparent exhaustion may develop. These are all signs of a very serious situation. If the body core temperature drops below 95 degrees, just 4 degrees below normal, immediate care is needed, as the person will likely become irrational. Once the body core temperature drops below 90 degrees, the person loses muscle control, and outside help is the person’s only hope for survival. If that help is not available, heart and/or respiratory failure and death will eventually follow as the core temperature continues to drop.

If a person is suffering from hypothermia, it is critically important that the person be warmed properly, or death may result. In a hypothermic person, cold blood is concentrated in the body extremities (arms and legs). If the extremities are warmed too quickly, this colder blood will be released into the body’s central core, possibly lowering the central core temperature to a fatal level. In other words, do not totally submerge a severely hypothermic person into a tub of warm water. Instead, keep the arms and legs out of the tub while warming the core, and gradually warm the extremities.

Frostbite is a condition in which the body tissue actually freezes. Frostbite is often associated with hypothermia. In a hypothermic person, the brain greatly reduces the amount of blood circulated into the extremities of the body which increases the chances the tissue at the end of the extremity may actually freeze. The most susceptible areas for frostbite include the fingers, toes, nose and earlobes.

As with the effects of cold and wind on people, any living thing, including outdoor animals also are affected. Even though fur provides the animals with a degree of protection, when exposed to prolong periods of wind with no shelter, animals will also succumb to the cold. Farmers need to move livestock to sheltered areas, and pet owners need to provide adequate shelters for outdoor pets.

For more effects of wind on the body, what precautions you can take to protect yourself and your family, and for a wind chill calculator, visit the National Weather Service at http:// www.nws.noaa.gov/om/windchill/ index.shtml.


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