Just as there are persistant hot places around the world, there are persistant cold places. The cold air alone can be deadly but when the air is moving if feels much colder. The wind chill is the effect of the wind on people and animals. The wind chill temperature is based on the rate of heat loss from exposed skin caused by wind and cold and is to give you an approximation of how cold the air feels on your body.
As the wind increases, it removes heat from the body, driving down skin temperature and eventually the internal body temperature. If the temperature is 0°F (-18°C) and the wind is blowing at 15 mph (13 kts), the wind chill temperature is -19°F (-28°C). At this level, exposed skin can freeze in just a few minutes.
|Wind Speed (mph)|
|Compute the Wind Chill
The only effect wind chill has on inanimate objects, such as car radiators and water pipes, is to shorten the amount of time for the object to cool. The inanimate object will not cool below the actual air temperature. For example, if the temperature outside is -5°F (-21°C) and the wind chill temperature is -31°F (-35°C), then your car's radiator temperature will be no lower than the air temperature of -5°F (-21°C).
The Wind Chill Chart
To determine the wind chill temperature, find the value closest to your outside air temperature. Find the value that most closely represents your present wind speed. Your wind chill temperature is the value where lines drawn from the air temperature and wind cross.
What is important about the wind chill besides feeling colder than the actual air temperature? The lower the wind chill temperature, the greater you are at risk for developing frost bite and/or hypothermia.
Frostbite occurs when your body tissue freezes. The most susceptible parts of the body are fingers, toes, ear lobes, and the tip of the nose. Hypothermia occurs when body core temperature, normally around 98.6°F (37°C) falls below 95°F (35°C). The following table shows how fast frostbite can occur at various wind chill temperatures.
The best way to avoid hypothermia and frostbite is to stay warm and dry indoors. When you must go outside, dress appropriately. Wear several layers of loose-fitting, lightweight, warm clothing. Trapped air between the layers will insulate you. Remove layers to avoid sweating and subsequent chill.
Outer garments should be tightly woven, water repellent, and hooded. Wear a hat, because half 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.
|Wind Chill||Cold Threat|
|40°F to 21°F (4°C to -6°C)||COLD. Unpleasant.|
|20°F to 1°F (-7°C to -17°C)||VERY COLD. Very unpleasant.|
|0°F to -19°F (-18°C to -28°C)||BITTER COLD. Frostbite possible. Exposed skin can freeze within 5 minutes.|
|-20°F to -69°F (-29°C to -56°C)||EXTREMELY COLD. Frostbite likely. Exposed skin can freeze within 1 minute. Outdoor activity becomes dangerous.|
|≤ -70°F (≤ -57°C)||FRIGIDLY COLD. Exposed skin can freeze in 30 seconds.|