4WX.com Weather Glossary

HEAT INDEX

HEAT INDEX (1) An index that combines air temperature and humidity to give an apparent temperature (eg. how hot it "feels"). Here is a heat index formula originally from Weatherwise magazine. It gives valid results above 70 deg. F. (-42.379+2.04901523*t+10.14333127*r-.22475541*t*r-(6.83783e-3)*t^2-(5.48 1717e-2)*r^2+(1.22874e-3)*t^2*r+(8.5282e-4)*t*r^2-(1.99e-6)*t^2*r^2)t=temp deg f and r=%rel hum HEAT INDEX (2) The combination of air temperature and humidity that gives a description of how the temperature feels. This is not the actual air temperature.