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# Wind Chill Index

## Effective Temperature of air in movement.

The convective heat loss due to wind can be dramatic. In the table below the wind chill effect is illustrated for air speeds up to 10 m/s (36 km/h, 2000 ft/min, 22 mph), or "fresh breeze" according the Beaufort wind scale.

Wind Chill Effect
Air SpeedChill Effect
(m/s)(ft/min)(oC)(oF)
0.1 20 0 0
0.25 50 0.5 2
1.5 300 4 7
3 600 6 10.5
5 1000 7 13
8 1575 8 15
10 2000 9 16

### Wind Chill Index - Wind Speed in km/h and Temperature in degrees Celsius

"Chilled" air temperature can be expressed as a function of wind speed and ambient air temperature

twC = 13.12 + 0.6215 ta - 11.37 v0.16 + 0.3965 ta v0.16                        (1)

where

twC = effective "wind" temperature (oC)

ta = air temperature (oC)

v = wind speed (km/h)

Wind Chill Index -  SI Units
"Chilled" Air Temperature (oC)
Ambient Air Temperature (oC)Wind Speed (km/h)
510152030405060
10 10 9 8 7 7 6 5 5
5 4 3 2 1 0 -1 -1 -2
0 -2 -3 -4 -5 -6 -7 -8 -9
-5 -7 -9 -11 -12 -13 -14 -15 -16
-10 -13 -15 -17 -18 -20 -21 -22 -23
-15 -19 -21 -23 -24 -26 -27 -29 -30
-20 -24 -27 -29 -30 -33 -34 -35 -36
-25 -30 -33 -35 -37 -39 -41 -42 -43
-30 -36 -39 -41 -43 -46 -48 -49 -50
-35 -41 -45 -48 -49 -52 -54 -56 -57
-40 -47 -51 -54 -56 -59 -61 -63 -64
• 1 km/h = 0.2778 m/s = 54.68 ft/min = 0.6214 mph = 0.5396 knot

### Wind Chill Index - Wind Speed in mph and Temperature in degrees Fahrenheit

The "Chilled" air temperature can also be expressed as a function of wind velocity and ambient air temperature as

twF = 35.74 + 0.6215 ta - 35.75 v0.16 + 0.4275 ta v0.16                        (2)

where

twF = effective temperature (oF)

ta = air temperature (oF)

v = wind speed (mph)

Wind Chill Index - Imperial Units
"Chilled" Air Temperature (oF)
Ambient Air Temperature (oF)Wind Speed (mph)
510152025303540
40 36 34 32 30 29 28 28 27
35 31 27 25 24 23 21 21 20
30 25 21 19 17 16 14 14 13
25 19 15 13 11 9 7 7 6
20 13 9 6 4 3 0 0 -1
15 7 3 0 -2 -4 -7 -7 -8
10 1 -4 -7 -9 -11 -14 -14 -15
5 -5 -10 -13 -15 -17 -21 -21 -22
0 -11 -16 -19 -22 -24 -27 -27 -29
-5 -16 -22 -26 -29 -31 -37 -34 -36
-10 -22 -28 -32 -35 -37 -41 -41 -43
-15 -28 -35 -39 -42 -44 -48 -48 -50
-20 -34 -41 -45 -48 -51 -55 -55 -57
-25 -40 -47 -51 -55 -58 -62 -62 -64
-30 -46 -53 -58 -61 -64 -69 -69 -71
-35 -52 -59 -64 -68 -71 -76 -76 -78
-40 -57 -66 -71 -74 -78 -82 -82 -84

Wind Chill Effects
Wind ChillPossible Effects
30oF or higher Generally unpleasant
30o to 15oF Unpleasant
14o to 0oF Very unpleasant
-1o to -20oF Frostbite possible
-21o to -60oF Frostbite likely - outdoor activities dangerous
-61o or lower Exposed flesh freezes within 30 seconds

## Related Topics

• ### Environment

Climate, meteorology, sun, wind and environmental related engineering resources.
• ### Physiology

Human physiology, air quality and comfort temperatures, activity and metabolic rates, health effects of carbon monoxide and more.

## Related Documents

• ### Beaufort's Wind Scale

The Beaufort description and observation scale for wind and wind speed.
• ### Convective Heat Transfer

Heat transfer between a solid and a moving fluid is called convection. This is a short tutorial about convective heat transfer.

• ### Hurricane Intensity Scale

The Saffir-Simpson hurricane damage potential scale.
• ### Survival Time in Cold Water

Time to exhaustion and death for humans in cold water.

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## Citation

• The Engineering ToolBox (2003). Wind Chill Index. [online] Available at: https://www.engineeringtoolbox.com/wind-chill-effect-d_112.html [Accessed Day Month Year].

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12.8.9