3.0 H
eat Stress Index Scale
The Heat Index is a valuable measure of the affect of humidity on how “hot it feels”. Since our bodies primary cooling mechanism is through perspiration and the cooling effect of evaporation from our skin; as the humidity increases, there is less evaporation and we feel hotter.
At a certain point, high Heat Index values become a health issue and a serious one for people who are working or exercising in it. The color LCD scale reflects the Heat Stress Index values and relates to the health affects outlined below:
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| IN RANGE |
| OUT OF RANGE |
Condition | Temperature | Heat Index / | Physical Response |
| Level | Humidex Value |
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Cold | Below 9.4°C/49°F |
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Cool | 10°C to 20°C |
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| 50°F to 69°F |
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Comfort | 21°C to 26°C |
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| 70°F to 79°F |
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Caution |
| 27°C to 31°C | • Fatigue possible with |
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| 80°F to 89°F | prolonged exposure and |
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| physical activity |
Extreme |
| 32°C to 40°C | • Sunstroke, muscle cramps |
Caution |
| 90°F to 104°F | and heat exhaustion are |
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| possible with prolonged |
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| exposure and physical |
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| activity |
Danger |
| 41°C to 53°C | • Sunstroke, muscle cramps |
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| 105°F to 129°F | and heat exhaustion are likely |
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| • Heat stroke possible with |
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| prolonged exposure and |
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| physical activity |
Extreme |
| 54°C/130°F or | • Heat stroke and |
Danger |
| higher | sunstroke likely |
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