# Heat Index Equations Formulas Calculator

Weather - Temperature - Heat Stroke Cramps Exhaustion - Medical

Solving for heat index. c1 = -42.379 c2 = -2.04901523 c3 = -10.14333127 c4 = -0.22475541 c5 = -6.83783 x 10-3 c6 = -5.481717 x 10-2 c7 = -1.22874 x 10-3 c8 = 8.5282 x 10-4 c9 = -1.99 x 10-6
The equation requires the temperature to be greater than 80 degrees Fahrenheit and the relative humidify to be above 40 percent. The equation approximates the heat index to within plus or minus 1.3 degrees Fahrenheit.

## Inputs:

dry bulb temperature (T)
relative humidity (R)

## Conversions:

dry bulb temperature (T)
= 0
= 0
fahrenheit
relative humidity (R)
= 0
= 0
percent

heat index (HI)
= NOT CALCULATED

## Other Units:

Physical Effect To Humans
 80 to 90 °F 80 to 90 °C caution Possible fatigue. Physical activity could lead to heat cramps. 90 to 105 °F 80 to 90 °C extreme caution Possible heat cramps and exhaustion. Physical activity could lead to heat stroke. 105 to 130 °F 80 to 90 °C danger Likely heat cramps and exhaustion. Probable heat stroke. above 130 °F 80 to 90 °C extreme danger Imminent heat stroke.

## Reference:

Wikimedia Foundation, Inc. Heat Index. 2010. http://en.wikipedia.org/wiki/Heat_index.

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