Wind Chill Chart
If you are looking for how to dress for Chicago weather, see The Chicago Weather Story
or the LOCAL FORECAST for Arlington Heights/Chicago.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" as developed to describe the relative discomfort/danger resulting from the combination of wind and temperature.
The wind chill index describes an equivalent temperature at which the heat loss from exposed flesh would be the same if the wind were near calm. For example, a wind chill index of -5 indicates that the affects of wind and temperature on exposed flesh are the same as if the air temperature were 5 degrees below zero eventhough the actual temperature is much higher.
The importance of the wind chill index is as an indicator of how to dress properly for winter weather. (Wind chill does not affect your car's antifreeze protection, freezing of water pipes, etc.) In dressing for cold weather an important factor to remember is that entrapped insulating air warmed by body heat is the best protection against the cold. Consequently, wear loose-fitting, lightweight, warm clothing in several layers. Outer garments should be tightly-woven, water-repellant and hooded. Mittens snug at the wrist are better protection than fingered gloves.
To use the chart, find the approximate temperature on the top of the chart. Read down until you are opposite the appropriate wind speed. The number which appears at the intersection of the temperature and wind speed is the wind chill index.
Wind Chill Chart Wind
(mph)Temperature (° F)
35
30
25
20
15
10
5
0
-5
-10
-15
-20
-25
5
32
27
22
16
11
6
0
-5
-10
-15
-21
-26
-31
10
22
16
10
3
-3
-9
-15
-22
-27
-34
-40
-46
-52
15
16
9
2
-5
-11
-18
-25
-31
-38
-45
-51
-58
-65
20
12
4
-3
-10
-17
-24
-31
-39
-46
-53
-60
-67
-74
25
8
1
-7
-15
-22
-29
-36
-44
-51
-59
-66
-74
-81
30
6
-2
-10
-18
-25
-33
-41
-49
-56
-64
-71
-79
-86
35
4
-4
-12
-20
-27
-35
-43
-52
-58
-67
-74
-82
-92
40
3
-5
-13
-21
-29
-37
-45
-53
-60
-69
-76
-84
-92
Wind speeds above 40 mph have little additional chilling affect
In using the table above, values of wind chill below -10° F are considered bitterly cold. Values of wind chill below -20° F are extremely cold -- human flesh will begin to freeze within one minute!
If you would like to calculate the wind chill index for combinations of temperature and wind other than those given in the table above, you can use the formula:
|
WC = 91.4 - (0.474677 - 0.020425 * V + 0.303107 * SQRT(V)) * (91.4 - T) |
||
|---|---|---|
|
where: |
WC
= wind chill index |
|
Source: National Weather Service
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