Dictionary
heat' in"dex
a number representing the effect of temperature and humidity on humans by combining the two variables into an “apparent” temperature, introduced as a replacement for the temperature-humidity index: a temperature of 90° and relative humidity of 65 percent combine to produce a heat index of 102.
Abbr.: H.I.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.