How is a heat index arrived at?
6News meteorologist Matt Sayers says the heat index takes into account not only the temperature, but also the moisture content in the air, or humidity. The human body uses sweat to naturally cool.
This process becomes less effective when the moisture content in the air is high, therefore making it "feel" hotter.
To alert the public to the dangers of exposure to extended periods of heat and the added effects of humidity, the National Weather Service has developed a Heat Index table, which can be found at: www.nws.noaa.gov/os/heat/index.shtml.
The Heat Index alerts the public to the likelihood of trouble related to prolonged exposure to heat and strenuous activity.