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# Heat Index Calculator

During hot summer days it sometimes feels hotter outside than the actual temperature suggests and it might very well be when you consider the “Heat Index”.

The heat index is a mathematical combination of air temperature and relative humidity which provides you the “how hot it really feels” temperature. Let me explain, when our bodies sweat the water evaporates carrying heat away from the skin allowing us to cool down, however when the humidity is high water does not evaporate as fast so the body retains more heat and you feel hotter. Below is a heat index conversion calculator so you can know the “how hot it really feels” temperature…..

### Calculate Heat IndexEnter temperature and relative humidity below to calculate heat index

Temperature:
Unit:
 F C
Relative Humidity:
Heat Index:

Looking for a deeper understanding? Below is the heat index equation….

HI = -42.379 + 2.04901523T + 10.14333127R – 0.22475541TR – 6.83783×10-3T2 – 5.481717×10-2R2 + 1.22874×10-3T2R + 8.5282×10-4TR2 – 1.99×10-6T2R2

HI = Heat Index
T = ambient dry bulb temperature (°F)
R = relative humidity (integer percentage)

For more read the “The Heat Index Equation” paper written by National Weather Service Meteorologist Lans P. Rothfusz.

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