Information on Wind Chill

What is the Wind Chill Factor?

The wind chill factor or wind chill index is a number, which expresses the cooling effect of moving air at different temperatures. It indicates in a very general way how many calories of heat are carried away from the surface of the body.

Who is associated with developing the concept of wind chill?

The Antarctic explorer, Paul A. Siple coined the term in his dissertation "Adaptation of the Explorer to the Climate of Antarctica," submitted in 1939. Siple was the youngest member of Admiral Byrd's Antarctica expedition in 1928-1930 and later made other trips to the Antarctic as part of Byrd's staff and for the United States Department of the Interior assigned to the United States Antarctic Expedition. He also served in many other endeavors related to the study of cold climates.

How is the wind chill index calculated?

Scientists have devised an equivalent temperature scale which makes it easy to determine the wind chill factor. Wind chill factors are supposed to measure the effect of the combination of wind speed and temperature uopn human comfort. There is nothing "exact about windchill. It is an estimation of apparent temperature. It is important to remember that these do not have the same effect on inanimate objects, or even on other animals or on plants. Nor is this effect felt by humans who are sheltered from the wind.

The following formula is one of serveral that can be used to calculate wind chill:

Wind chill = 91.4 - (0.474677 - 0.020425 * W + 0.303107 * SQRT(W)) * (91.4 - T)

where W = wind speed (mph) & T = temperature (°F)

The chart shown below illustrates common wind chill values. Find the wind speed in the column on the left and find the temperature reading in the horizontal row at the top. The intersection of these two points gives the corresponding wind chill factor.

Wind Chill Chart
Wind
Speed
(mph)		 Air Temperature
(Degrees Fahrenheit)
4035302520151050-5-10-15-20-25-30-35-40-45
5 35 33 27 21 16 12 7 1 -6 -11 -15 -20 -26 -31 -35 -41 -47 -54
10 30 21 16 9 2 -2 -9 -15 -22 -27 -31 -38 -45 -52 -58 -64 -70 -77
15 25 16 11 1 -6 -11 -18 -25 -33 -40 -45 -51 -60 -65 -70 -78 -85 -90
20 20 12 3 -4 -9 -17 -24 -32 -40 -46 -52 -60 -68 -76 -81 -88 -96 -103
25 15 7 0 -7 -15 -22 -29 -37 -45 -52 -58 -67 -75 -83 -89 -96 -104 -112
30 10 5 -2 -11 -18 -26 -33 -41 -49 -56 -63 -70 -78 -87 -94 -101 -109 -117
35 10 3 -4 -13 -20 -27 -35 -43 -52 -60 -67 -72 -83 -90 -98 -105 -113 -123
40 10 1 -4 -15 -22 -29 -36 -45 -54 -62 -69 -76 -87 -94 -101 -107 -116 -128
LITTLE DANGER INCREASING DANGER GREAT DANGER
Note: Wind speeds greater than 40 mph or less than 4 mph have little effect on the wind chill.
LITTLE DANGER | There is little danger if clothed properly.
INCREASING DANGER | There is increasing danger of freezing exposed skin.
GREAT DANGER | There is great danger of freezing exposed skin.


A Wind Chill Index calculator
& temperature converter.
(You must have Java Script enabled in your browser.)

Compute Wind Chill Index
Temperature (Fahrenheit)
Wind Speed (mph)
Wind Chill Index =
To convert, enter values in either box.
degrees Celsius
equals
degrees Fahrenheit


How can the cold affect you?

Now that you know how cold it can get, two things you should be concerned about are frostbite and hypothermia.

FROSTBITE
Frostbite is the crystallization of tissue fluid cased by exposure to temperatures below freezing. The most common areas affected are the face, nose, ears, hands and feet. Symptoms include: redness and pain in the early stages, followed by a waxy white appearance, numbness, and the skin may feel stiff and even brittle.

HYPOTHERMIA
Hypothermia is a condition that occurs when the body's internal temperature drops steadily. The onset of hypothermia begins when the core temperature dips below 95°F. If this condition is not reversed it can bring fatal consequences. Hypothermia can develop with little warning and is generally characterized by uncontrollable shivering. Mild hypothermia can be treated by drinking warm liquids or by taking a hot shower. A more serious condition requires medical attention.
PREVENTION OF COLD INJURY
  • Use the Buddy system, this is the best way to prevent cold injury.
  • If you begin to feel cold do some exercises until you start feeling warm again.
  • Dress for the weather and avoid getting wet or damp.

To stay warm remember the word C-O-L-D
CCleanliness and Care: Feet, socks, and clothing are warmer when clean. Good foot care is essential.
OOverheating: Prevent overheating by adjusting your clothing to the job being performed.
LLoose and Layered: Loose-fitting clothing ensures good circulation and insulation. Layered clothing provides air spaces which hold body heat and allows you to adjust the number of layers to be proportional to the temperature and activity being performed.
DDampness: Any wet garment is a cold garment, just as tight-fitting garments are cold producing garments. Keep clothing dry.

FIRST AID FOR COLD INJURIES

  • Get individual off their feet.
  • Get individual into warm dry clothing.
  • Get individual warm fluids to drink (NO ALCOHOLIC BEVERAGES)
  • Do not smoke.
  • Keep the effected area clean, warm and dry. Do not allow to REFREEZE. If you cannot keep area warm, leave it frozen.
  • Do not rub effected area.
  • Evacuate through medical channels as soon as possible.

Sources: Weatherwise, vol. 34 (December 1981), p. 266; Who Was Who in American History: Science and Technology, p. 557, and Gene Nygaard's Wind chill factors.
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