Hall's Harbour Observatory,   Hall's Harbour, NS

Windchill Calculations

21-Nov-2017, 19:05 AST 21-Nov-2017, 23:05 UTC

Page contents:   Online Calculator - Table (New) - Table (Old) - About Wind Chill


Wind Chill Calculator

Temp: °C
Wind: km/h
New (2001) calculationOld (pre-2001) calculation
Equiv °C:
W/m2:

Note that Environment Canada does not use units on the new windchill indices. Both the 2-digit ("Equiv °C") and the 4-digit ("W/m2") indices are actually dimensionless numbers. The numbers are calibrated to correspond approximately to the old windchill indices, which were given with units.

Caution should be used in outdoor activities when the wind chill is more than 1500 W/m2. Outdoor activities should be curtailed when the wind chill is more than 2000 W/m2. Anyone required to work outdoors at wind chill values over 2000 W/m2 should be allowed to warm up every 15 minutes.


New (2001) Wind Chill Calculation

(4-digit and 2-digit dimensionless values)
Wind
(km/h)
Temp (°C)
5 0 -5 -10 -15 -20 -25 -30 -35 -40 -45
10 945
3
1080
-3
1215
-9
1345
-15
1480
-21
1610
-27
1740
-33
1870
-39
2000
-45
2130
-51
2260
-57
20 980
1
1125
-5
1265
-12
1405
-18
1545
-24
1685
-30
1820
-37
1960
-43
2095
-49
2230
-56
2365
-62
30 1005
0
1150
-6
1295
-13
1440
-20
1585
-26
1730
-33
1870
-39
2015
-46
2155
-52
2295
-59
2435
-65
40 1020
-1
1170
-7
1320
-14
1470
-21
1615
-27
1765
-34
1910
-41
2055
-48
2200
-54
2340
-61
2485
-68
50 1035
-1
1190
-8
1340
-15
1490
-22
1640
-29
1790
-35
1940
-42
2085
-49
2235
-56
2380
-63
2525
-69
60 1050
-2
1205
-9
1355
-16
1510
-23
1660
-30
1815
-36
1965
-43
2115
-50
2265
-57
2410
-64
2560
-71
70 1060
-2
1215
-9
1370
-16
1525
-23
1680
-30
1835
-37
1985
-44
2140
-51
2290
-58
2440
-65
2590
-72

Old (pre-2001) Wind Chill Calculation

(W/m2 and apparent °C)
Wind
(km/h)
Temp (°C)
5 0 -5 -10 -15 -20 -25 -30 -35 -40 -45
10 795
3 °C
935
-2 °C
1075
-7 °C
1215
-13 °C
1360
-18 °C
1500
-23 °C
1640
-28 °C
1785
-34 °C
1925
-39 °C
2065
-44 °C
2210
-50 °C
20 925
-2 °C
1090
-8 °C
1255
-14 °C
1425
-20 °C
1590
-26 °C
1755
-33 °C
1920
-39 °C
2085
-45 °C
2250
-51 °C
2415
-57 °C
2580
-63 °C
30 1010
-5 °C
1190
-11 °C
1370
-18 °C
1550
-25 °C
1730
-32 °C
1905
-38 °C
2085
-45 °C
2265
-52 °C
2445
-58 °C
2625
-65 °C
2805
-72 °C
40 1060
-7 °C
1250
-14 °C
1440
-21 °C
1630
-28 °C
1820
-35 °C
2010
-42 °C
2200
-49 °C
2390
-56 °C
2580
-63 °C
2770
-71 °C
2960
-78 °C
50 1100
-8 °C
1295
-15 °C
1490
-23 °C
1690
-30 °C
1885
-37 °C
2080
-45 °C
2275
-52 °C
2475
-59 °C
2670
-67 °C
2865
-74 °C
3060
-81 °C
60 1125
-9 °C
1325
-17 °C
1525
-24 °C
1725
-32 °C
1925
-39 °C
2125
-47 °C
2330
-54 °C
2530
-62 °C
2730
-69 °C
2930
-77 °C
3130
-84 °C
70 1140
-10 °C
1340
-17 °C
1545
-25 °C
1750
-32 °C
1955
-40 °C
2155
-48 °C
2360
-55 °C
2565
-63 °C
2765
-70 °C
2970
-78 °C
3175
-86 °C

A general note about wind chill

It is a common misconception that a wind chill of, for example, -50 will cool an object to a final temperature of -50°C. This is false! Windchill can never cool any object below the actual air temperature. If the temperature is -33°C and the wind is 30 km/h, producing a windchill index of -50, the coldest that any object left outdoors will ever get is -33°C.

Wind chill affects the cooling rate of an object that is warmer than the air temperature, not its final temperature. Wind chill has absolutely no effect on objects that are already at air temperature.

For example, a recently-parked car will lose heat faster than human skin, because the car's radiator is considerably warmer than body temperature. When the temperature of the radiator drops to skin temperature, its rate of heat loss will be similar to the rate of heat loss from human skin. As the temperature of the radiator drops further, its rate of heat loss will continue to decrease until its temperature reaches the air temperature, at which point the heat loss reaches zero. Because it is no longer losing heat, the temperature will not drop any further.

This is a consequence of the Second Law of Thermodynamics. Without a source of additional energy, such as a heat pump, heat can only flow from a warmer object to a cooler object. For car radiator to cool below the air temperature, heat would have to flow from the cooler object (the radiator) to the warmer object (the air). That would be a violation of the Second Law.