Heat index is a derived value based on the current Temperature and the Dew Point. A high heat index is to hot as the Wind Chill is to cold. A high Dew Point temperature means that the amount of moisture in the air is high. The high humidity prevents your sweat from evaporating, which in turn makes you retain more heat. Obviously, the more heat you retain, the warmer you get!
High Heat Indices can mean trouble for people with lung problems, children and the elderly. Heat exhaustion, cramps, dehydration and even heat stroke can occur with exposure to Heat Indices over 105°F.
Persons working outside or in enclosed areas should stay hydrated by drinking lots of water, and try to avoid exposure to the sun. If you feel dizzy or nauseous, stop what you are doing, take a break and get into a cooler area like an air-conditioned building.
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