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To use this calculator select the required parameters and enter the temperature and wind speed.
Note that the metric Wind Chill is
only defined for temperatures in the range
- 45oC to
+4.4 oC and wind speeds 5 to 100 km/hr.
Formula for metric wind chill calculation
Twind_chill = 13.12 + 0.6215*T - 11.37*(v0.16) +
0.3965*T*(v0.16)
Wind chill temperature is a measure of the combined cooling
effect of wind and temperature.
As wind increases, heat is carried
away from the body at a faster rate,
driving down both the skin
temperature (which can cause frostbite)
and eventually the internal
body temperature (which can kill).
The Wind Chill Temperature index
is the measure of this relationship.
The wind chill index combines the temperature with the wind speed to indicate how cold it actually feels outside, particularly to unprotected skin exposed to the wind.
History:
The earliest wind chill index
was based on the research of Antarctic explorers Siple and Passel
who first measured the combined impacts of varying wind speed and
freezing temperatures in 1945. They did this by measuring heat loss
from water as it froze in a plastic container suspended from a tall
pole.
For over a year, there have been discussions between the National Weather Service and the Meteorological Services of Canada about updating the Wind Chill Temperature Index. During the Autumn of 2000, a special group consisting of the National Weather Service, the Meteorological Services of Canada and the International Society of Biometeorology evaluated the existing wind chill formula and made changes to improve it. The group's goal was to internationally upgrade and standardize the Wind Chill Temperature Index.
The new Wind Chill Temperature Index, by Randall Osczevski of DCIEM and Maurice Bluestein of Purdue University in Indiana, makes use of advances in science, technology and computer modelling to provide a more accurate,understandable and useful formula for estimating the dangers arising from winter winds and freezing temperatures. In addition, clinical trials were conducted and the results of those trials has been used to verify and improve the accuracy of the new formula.
Twelve volunteers (six men and six women) participated in the
clinical trials.
These consisted in four walks, at 4.8 km/h, on a
treadmill in a refrigerated wind tunnel at the Defence and Civil
Institute of Environmental Medicine in Toronto, Canada: one walk at
each of -10, 0 and +10 deg C, plus a "wet trial" at +10 deg C during which
participants received, every 15 seconds, a light one-second splash
of water in their faces. During each 90-minute walk, the volunteers
were walking while facing a wind of 2 metres per second (m/s) for 30
minutes, followed by 30 minutes at 5 m/s, and 30 minutes at 8 m/s
(or about 4, 10 and 16 mph, respectively). Sensors were fixed to
participants' forehead, cheeks, chin and nose, as well as to the
inside of one cheek, to measure skin temperature and heat loss. The
results from these trials were used to determine the various
thresholds for frostbite, as seen on the new wind chill chart.
The new wind chill equation is now in use in both Canada and the United States. Therefore, there is now a consistent wind chill formula across North America.
The Wind Chill Temperature Index has been implemented in Canada and the United States, resulting in a consistent index provided to help the public protect itself against the dangers of frostbite and hypothermia.
Specifically, the new Wind Chill Temperature Index:
1: uses calculated wind speed at an average height of five feet
(typical height of a human face) based on readings from the
national standard height of 33 feet (typical height of an
anemometer)
2: is based on the latest heat transfer theory, i.e., heat loss
from the body to its surroundings, during cold and breezy/windy
days;
3: is based on a human face model because this is the part of the
human body most often exposed to the elements
4: uses a standard factor for skin tissue and assumes a no
sunlight scenario.
Frostbite Threshold:
For the
first time, the wind chill temperatures include specific threshold
values that provide specific warning of time-to-frostbite at given
levels of wind chill. For example, a temperature of 5 degrees
Fahrenheit and a wind speed of 30 mph equal a wind chill of -19,
which will produce frostbite in 30 minutes. The chart also shows how
frostbite will occur sooner if the temperature is lower or the wind
speed higher.
A simple experiment to better understand wind chill.
Turn on a fan and stand in front of it. You will feel colder because of the wind cooling your skin, but the temperature
in the room has not changed. You cannot make the room any colder, no matter how high you turn up the fan. Just like outside,
no matter how strong the wind blows, the temperature of the air outside does not change.
Dab some water on your skin and stand in front of the fan again. The wet skin should feel much colder.
This demonstrates how important it is to stay dry when outdoors in cold and windy conditions.
This calculator is based upon the revised formula of August 2,
2001,which is available at
http://www.erh.noaa.gov/er/iln/tables.htm.
- Once you have estimated the wind speed and you know the temperature outside, you can estimate the wind chill by referring to the numerical chart below.
|
Wind Speed (km/h)
|
What to Look for When Estimating Wind Speed
|
Temperature (°C)
|
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
|
0
|
-5
|
-10
|
-15
|
-20
|
-25
|
-30
|
-35
|
-40
|
-45
|
||
| 10 | Wind felt on face; wind vane begins to move. | -3 | -9 | -15 | -21 | -27 | -33 | -39 | -45 | -51 | -57 |
| 20 | Small flags extended. | -5 | -12 | -18 | -24 | -30 | -37 | -43 | -49 | -56 | -62 |
| 30 | Wind raises loose paper, large flags flap and small tree branches move. | -6 | -13 | -20 | -26 | -33 | -39 | -45 | -52 | -59 | -65 |
| 40 | Small trees begin to sway and large flags extend and flap strongly. | -7 | -14 | -21 | -27 | -34 | -41 | -48 | -54 | -61 | -68 |
| 50 | Large branches of trees move, telephone wires whistle and it is hard to use an umbrella. | -8 | -15 | -22 | -29 | -35 | -42 | -49 | -56 | -63 | -69 |
| 60 | Trees bend and walking against the wind is hard. | -9 | -16 | -23 | -30 | -36 | -43 | -50 | -57 | -64 | -71 |
| Wind Chill | Risk of Frostbite | Other Health Concerns |
What to Do |
|---|---|---|---|
| 0 to -9 | Low |
|
|
| -10 to -27 | Low |
|
|
| -28 to -39 | Risk: exposed skin can freeze in 10 to 30 minutes |
|
|
| -40 to -47 | High risk: exposed skin can freeze in 5 to 10 minutes* |
|
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| -48 to -54 | Very High risk: exposed skin can freeze in 2 to 5 minutes* |
|
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| -55 and colder | Extremely High risk: exposed skin can freeze in less than 2 minutes* |
|
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*In sustained winds over 50 km/h, frostbite can occur faster than indicated.
Source: Environment Canada. www.ec.gc.ca
Wind Chill Calculation Chart
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Wind Chill Calculator. ( 8 pages )
by Romsey Australia is licensed under a Creative Commons Attribution 2.5 Australia License.
Revised December 2010