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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.

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)

"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)

"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 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 resources
• Physiology - Human physiology, air quality and comfort temperatures, activity and metabolic rates, health effects of carbon monoxide and more

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Temperature

oC
oF

Length

m
km
in
ft
yards
miles
naut miles

Area

m2
km2
in2
ft2
miles2
acres

Volume

m3
liters
in3
ft3
us gal

Weight

kgf
N
lbf

Velocity

m/s
km/h
ft/min
ft/s
mph
knots

Pressure

Pa (N/m2)
bar
mm H2O
kg/cm2
psi
inches H2O

Flow

m3/s
m3/h
US gpm
cfm

1 14