Prolonged exposure to severe cold can result in hypothermia and/or tissue necrosis. It is important to keep the core body temperature from falling below 96.8 degrees Fahrenheit, and to prevent cold injury to the extremities or exposed body parts.
As the wind speed increases, there is an additional cooling effect, decreasing the effective temperature to the exposed individual. The effect increases until wind speeds reach 40 miles per hour, after which there is little additional effect. Tissue freezing will occur only at temperatures below 30.2 degrees Fahrenheit, regardless of wind speed. The presence of wetting greatly increases the risk for hypothermia and must be aggressively prevented.
Table of Effective Temperature Experienced for a Given
Temperature in °F and Wind Speed in miles per hour
|
Windmph |
50 °F |
40 °F |
30 °F |
20 °F |
10 °F |
0 °F |
-10 °F |
-20 °F |
-30 °F |
-40 °F |
-50 °F |
-60 °F |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
0 |
50 |
40 |
30 |
20 |
10 |
0 |
-10 |
-20 |
-30 |
-40 |
-50 |
-60 |
|
5 |
48 |
37 |
27 |
16 |
6 |
-5 |
-15 |
-26 |
-36 |
-47 |
-57 |
-68 |
|
10 |
40 |
28 |
16 |
4 |
-9 |
-24 |
-33 |
-46 |
-58 |
-70 |
-83 |
-95 |
|
15 |
36 |
22 |
9 |
-5 |
-18 |
-32 |
-45 |
-58 |
-72 |
-85 |
-99 |
-112 |
|
20 |
32 |
18 |
4 |
-10 |
-25 |
-39 |
-53 |
-67 |
-82 |
-96 |
-110 |
-121 |
|
25 |
30 |
16 |
0 |
-15 |
-29 |
-44 |
-59 |
-74 |
-88 |
-104 |
-118 |
-133 |
|
30 |
28 |
13 |
-2 |
-18 |
-33 |
-48 |
-63 |
-79 |
-94 |
-109 |
-125 |
-140 |
|
35 |
27 |
11 |
-4 |
-20 |
-35 |
-51 |
-67 |
-82 |
-98 |
-113 |
-129 |
-145 |
|
40+ |
26 |
10 |
-6 |
-21 |
-37 |
-53 |
-69 |
-85 |
-100 |
-116 |
-132 |
-148 |
Equation with Wind Speed Constant
effective temperature in °F at a given wind speed in miles per hour =
= (a * (temperature)) + b
|
wind speed in mph |
a |
b |
|---|---|---|
|
0 |
1 |
0 |
|
5 |
1.051049 |
-4.744755 |
|
10 |
1.2293706 |
-21.35315 |
|
15 |
1.3437063 |
-31.53147 |
|
20 |
1.4108392 |
-38.6958 |
|
25 |
1.4832168 |
-44.08392 |
|
30 |
1.5286713 |
-48.18998 |
|
35 |
1.5601399 |
-51.03263 |
|
40 |
1.5793706 |
-53.01981 |
Equation with External Temperature Constant
wind speed < 10 miles per hour
effective temperature for a given external temperature =
= (a * ((wind speed in mph) ^2)) + (b * (wind speed in mph)) + c
|
external temperature |
a |
b |
c |
|---|---|---|---|
|
-60 °F |
-0.38 |
0.3 |
-60 |
|
-50 °F |
-0.38 |
0.5 |
-50 |
|
-40 °F |
-0.32 |
0.2 |
-40 |
|
-30 °F |
-0.32 |
0.4 |
-30 |
|
-20 °F |
-0.20 |
0.2 |
-20 |
|
-10 °F |
-0.26 |
0.3 |
-10 |
|
0 °F |
-0.28 |
0.4 |
0 |
|
10 °F |
-0.22 |
0.3 |
10 |
|
20 °F |
-0.16 |
0 |
20 |
|
30 °F |
-0.16 |
0.2 |
30 |
|
40 °F |
-0.12 |
0 |
40 |
|
50 °F |
-0.12 |
0.2 |
50 |
Equation with External Temperature Constant
wind speed >= 10 miles per hour
effective temperature for a given external temperature =
= (a * ((wind speed in mph) ^3)) + (b * ((wind speed in mph) ^2)) + (c * (wind speed in mph)) + d
|
external temperature |
a |
b |
c |
d |
|---|---|---|---|---|
|
-60 °F |
-0.000222 |
0.0642857 |
-4.501587 |
-56.64286 |
|
-50 °F |
-0.000889 |
0.1152381 |
-5.525397 |
-38.57143 |
|
-40 °F |
-0.000889 |
0.1095238 |
-5.011111 |
-18.14286 |
|
-30 °F |
-0.001111 |
0.1314286 |
-5.772222 |
-24.28571 |
|
-20 °F |
-0.000667 |
0.087619 |
-4.278571 |
-11.28571 |
|
-10 °F |
-0.000889 |
0.1019048 |
-4.430159 |
1.8571429 |
|
0 °F |
-0.000222 |
0.0414286 |
-2.573016 |
-2.142857 |
|
10 °F |
-0.000667 |
0.0785714 |
-3.461905 |
18.428571 |
|
20 °F |
-0.000444 |
0.0614286 |
-2.96746 |
27.785714 |
|
30 °F |
-0.000667 |
0.0709524 |
-2.880952 |
38.428571 |
|
40 °F |
-0.000444 |
0.0490476 |
-2.119841 |
44.571429 |
|
50 °F |
-0.000222 |
0.0309524 |
-1.549206 |
52.714286 |
|
Effective Temperature |
Interpretation |
|---|---|
|
above –25°F |
there is little danger of freezing with short periods of exposure if skin dry |
|
between -25 and -74 °F |
this is a zone of increasing danger, with exposed flesh freezing within 1 minute |
|
below -74 °F |
this is a zone of great risk, with flesh freezing within 30 seconds of exposure |
Specialty: Emergency Medicine, Critical Care
ICD-10: ,
