![[ Rescue Dynamics Logo ]](../images/resqlogo.gif)
Outdoor Article of the Month - June 1997
Humidex: It's Not Just the Heat!
Outdoor Article of the Month - June 1997
Humidex: It's Not Just the Heat!
We likely all realize that hot summer days feel much worse when the humidity is high. This is related to the cooling effects of evaporation when we perspire. When the humidity is high, our perspiration evaporates more slowly and we feel warmer. When the combination of temperature and humidity is very high, we are actually at more risk from heat illness such as heat cramps, heat exhaustion and heat stroke. In 1965, Canadian meteorologists devised a scale called the Humidex that attempts to take both heat and humidity into account to give us a single value that we can use to help guide our actions on hot and humid days.
Most locations in Canada do not experience extreme Humidex values, but it is possible that any given location could reach temperatures where great caution is advised. In countries having areas with more tropical climates, extreme Humidex values are much more common. Readings in the mid to high 30s should signal caution and reduction of vigorous exercise as well as altering clothing. If working or recreating outdoors, frequent rest breaks in the shade are warranted as well as drinking plenty of fluids. Replenishing electrolytes with any of a number of sport drinks currently available is useful.
At extremely high values of 40 degrees or more, heatstroke is increasingly likely. People should stay out of the heat and stop unnecessary activities. Heatstroke is a potentially life threatening problem and first aid assistance should be given immediately. Contact emergency personnel immediately.
Humidex
25%
30%
40%
50%
60%
70%
80%
90%
100%
38
42
43
47
54
57
*
*
*
*
37
40
42
45
49
54
55
58
*
*
36
39
40
43
47
51
56
57
58
*
35
37
38
42
45
48
51
54
57
*
34
36
37
41
43
47
49
52
55
58
33
34
36
38
42
44
47
50
52
55
32
33
34
37
39
42
45
47
50
52
31
31
33
35
38
40
43
45
48
50
30
31
31
34
36
38
41
43
46
48
29
29
30
32
34
37
38
41
44
46
28
28
29
31
33
35
37
39
41
45
27
27
28
29
31
33
35
37
39
41
26
26
27
28
29
31
33
35
37
39
25
25
26
27
28
30
32
33
35
37
24
24
25
26
27
28
30
32
33
35
23
23
23
24
25
27
28
30
32
33
* = Beyond the Earth atmosphere's ability to hold water vapor.
Danger Category
Humidex
Extreme Danger
> 55
Heatstroke imminent with continued exposure.
Danger
40 - 54
Great discomfort. Avoid exertion. Seek a cool shady location. Heat cramps or heat exhaustion likely. Heat stroke possible with continued exposure and / or physical activity.
Extreme Caution
30 - 39
Some discomfort. Heatstroke, heat exhaustion and heat cramps possible with prolonged exposure and / or physical activity.
Caution
< 29
Little discomfort. Fatigue possible with prolonged exposure and / or physical activity.
Rescue Dynamics Copyright © 1997 Cyril Shokoples
![[Made with Macintosh Icon]](../images/macmadeg4.gif){kind=small}
Further Information, Comments, Suggestions?
5109 - 17A Avenue NW
Edmonton, AB, Canada T6L 1K5
phone (780) 461-5040 voice / fax
All rights reserved. Terms & Conditions apply.
Last updated
