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What is the heat index?

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...

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