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Compare wind chill and heat index side by side with reference charts and risk levels.
Wind chill and heat index are both "feels like" temperature metrics. Wind chill accounts for heat loss from wind in cold weather; heat index accounts for reduced sweat evaporation in humid heat.
Wind Chill Chart (°F)
| Temp\Wind | 5 | 10 | 15 | 20 | 25 | 30 |
|---|---|---|---|---|---|---|
| 20°F | 13 | 8.9 | 6.2 | 4.2 | 2.6 | 1.3 |
| 30°F | 24.7 | 21.2 | 19 | 17.4 | 16 | 14.9 |
| 40°F | 36.5 | 33.6 | 31.8 | 30.5 | 29.4 | 28.5 |
| 50°F | 48.2 | 46 | 44.6 | 43.6 | 42.8 | 42 |
Heat Index Chart (°F)
| Temp\RH | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|
| 80°F | 80 | 81 | 82 | 83 | 84 | 86 |
| 85°F | 84 | 87 | 89 | 93 | 97 | 102 |
| 90°F | 91 | 95 | 100 | 106 | 113 | 122 |
| 95°F | 99 | 105 | 113 | 123 | 134 | 147 |
| 100°F | 109 | 118 | 130 | 143 | 158 | 176 |
| 105°F | 122 | 134 | 149 | 166 | 187 | 209 |
Formula
WC = 35.74 + 0.6215T - 35.75V^0.16 + 0.4275TV^0.16 | HI = Rothfusz polynomial(T, RH)T = Air temperature in °F
V = Wind speed in mph (wind chill)
RH = Relative humidity in % (heat index)
Worked Example
Wind Chill at 20°F, 25 mph wind
Did you know? The NWS wind chill formula was updated in 2001 after clinical trials where volunteers walked on treadmills in a refrigerated wind tunnel at the University of Manitoba. The heat index formula dates to a 1979 study by Robert Steadman.
Sources
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