National Weather Service Wind-Chill Table (U.S. Units) (updated 10/11/08)

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How cold is it outside? Simply knowing the temperature doesn't tell you enough about the conditions to enable you to dress sensibly for all winter weather. Other factors including wind speed, relative humidity and sunshine play important roles in determining how cold you feel outside. A description of the character of weather known as "coldness" was proposed about 1940 by scientists working in the Antarctic. The "wind chill index" was developed to describe the relative discomfort/danger resulting from the combination of wind and temperature.

On November 1, 2001, the National Weather Service began using a new wind chill index. The reason for the change is to improve upon the current index, which is based on the 1945 Siple and Passel Index. During the Fall of 2000, the Office of the Federal Coordinator for Meteorological Services and Supporting Research (OFCM) formed a special group consisting of several Federal agencies, MSC, the academic research community (Indiana University-Purdue University in Indianapolis (IUPUI), University of Delaware, and University of Missouri), and the International Society of Biometeorology. Their job was to evaluate the existing wind chill formula and make necessary changes to improve upon it.

The new wind chill formula makes use of the advances in science, technology, and computer modeling to provide a more accurate, understandable, and useful formula for calculating wind chill. The new wind chill index uses wind speed calculated at the average height (5 feet) of the human body's face instead of 33 feet (the standard anemometer height); be based on a human face model; incorporate modern heat transfer theory (heat loss from the body to its surroundings, during cold and breezy/windy days); lower the calm wind threshold to 3 mph; use a consistent standard for skin tissue resistance; and assume the worst case scenario for solar radiation (clear night sky). In 2002, adjustments for solar radiation (i.e., the impact of sun) for a variety of sky conditions (sunny, partly sunny and cloudy) were added to the calculation model.

Wind chill does not affect your car's antifreeze protection. It has an impact on how quickly your home's exposed water pipes freeze, but has little impact on whether they would freeze or not. The importance of the wind chill index is as an indicator of how to dress properly for winter weather. For more information, see the National Weather Service website--http://www.weather.gov/os/windchill/index.shtml

Temperature (Fahenhiet), wind speed (miles per hour)
and the equivalent temperature on exposed skin.
Calm
10 MPH
15 MPH
20 MPH
25 MPH
30 MPH
35 MPH
40 MPH
45 MPH
50 MPH
55 MPH
60 MPH

40 degrees

34
32
30
29
28
28
27
26
26
25
25

35 degrees

27
25
24
23
22
21
20
19
19
18
17

30 degrees

21
19
17
16
15
14
13
12
12
11
10

25 degrees

15
13
11
9
8
7
6
5
4
4
3

20 degrees

9
6
4
3
1
0
-1
-2
-3
-3
-4

15 degrees

3
0
-2
-4
-5
-7
-8
-9
-10
-11
-11

10 degrees

-4
-7
-9
-11
-12
-14
-15
-16
-17
-18
-19

5 degrees

-10
-13
-15
-17
-19
-21
-22
-23
-24
-25
-26

0 degrees

-16
-19
-22
-24
-26
-27
-29
-30
-31
-32
-33

-5 degrees

-22
-26
-29
-31
-33
-34
-36
-37
-38
-39
-40

-10 degrees

-28
-32
-35
-37
-39
-41
-43
-44
-45
-46
-48

-15 degrees

-35
-39
-42
-44
-46
-48
-50
-51
-52
-54
-55

-20 degrees

-41
-45
-48
-51
-53
-55
-57
-58
-60
-61
-62

-25 degrees

-47
-51
-55
-58
-60
-62
-64
-65
-67
-68
-69

-30 degrees

-53
-58
-61
-64
-67
-69
-71
-72
-74
-75
-76

-35 degrees

-59
-64
-68
-71
-73
-76
-78
-79
-81
-82
-84

-40 degrees

-66
-71
-74
-78
-80
-82
-84
-86
-88
-89
-91

Wind-Chill Table (International Units of Measurements)

Temperature (Celsius), wind speed (kilometers per hour)
and the equivalent temperature on exposed skin.

Calm
16 KPH
24 KPH
32 KPH
40 KPH
48 KPH
56 KPH
64 KPH

2 degrees

-1 degrees

-4 degrees

-7 degrees

-9 degrees

-12 degrees

-15 degrees

-18 degrees

-21 degrees

-23 degrees

-26 degrees

-29 degrees

-32 degrees

-34 degrees

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