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 Speed | Chill 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) | |||||||
| 5 | 10 | 15 | 20 | 30 | 40 | 50 | 60 | |
| 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
Download and print Wind Chill Index chart
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) | |||||||
| 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | |
| 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 |
Download and print Wind Chill Index chart
| Wind Chill | Possible Effects |
|---|---|
| 30 oF or higher | Generally unpleasant |
| 30o to 15 oF | Unpleasant |
| 14o to 0 oF | Very unpleasant |
| -1o to -20 oF | Frostbite possible |
| -21o to -60 oF | Frostbite likely - outdoor activities dangerous |
| -61o or lower | Exposed flesh freezes within 30 seconds |
