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What Is The Heat Index?

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enotes | Valedictorian

Posted October 9, 2011 at 4:00 PM via web

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What Is The Heat Index?

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fact-finder | Valedictorian

Posted October 10, 2011 at 4:00 PM (Answer #1)

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The heat index, also called the humiture index or temperature-humidity index, is a way to measure how hot and muggy it feels. This index gives an indication of how stressful outdoor activity will be for the average person.

The heat index is most useful during the hottest part of the day. The lower the heat index, the more comfortable the air is. Any value over 89 is considered to be muggy and uncomfortably hot. Heat exhaustion and sunstroke are of greatest concern when the heat index reaches 105. The chart below provides the heat index for some temperatures and relative humidities (the amount of moisture in the air at a given temperature).

Air Temperature (°F)
70 75 80 85 90 95 100 105 110 115 120
Relative Humidity Feels like(°F)
0% 64 69 73 78 83 87 91 95 99 103 107
10% 65 70 75 80 85 90 95 100 105 111 116
20% 66 72 77 82 87 93 99 105 112 120 130
30% 67 73 78 84 90 96 104 113 123 135 148
40% 68 74 79 86 93 101 110 123 137 151
50% 69 75 81 88 96 107 120 135 150
60% 70 76 82 90 100 114 132 149
70% 70 77 85 93 106 124 144
80% 71 78 86 97 113 136
90% 71 79 88 102 122
100% 72 80 91 108

 

Sources: Engelbert, Phillis. The Complete Weather Resource, vol. 3, pp. 424-25; World Almanac 1996, p.186

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