The heat index formula is expressed as,
HI= c1+c2T+c3R+c4TR+c5T2+c6R2+c7T2R+c8TR2+c9T2R2
In this formula,
HI = heat index in degrees Fahrenheit
R = Relative humidity
T = Temperature in ∘F
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
It is found that whenever HI values exceed above 40∘C during different temperature and humidity ranges, there is a threat of heatstroke.
Solved Examples
Example 1
Determine the heat index if the temperature is 197∘F and the relative humidity is 80%.
Solution:
Given:
T = 197∘F,
R = 80%
Substituting the values in the given formula,
HI= c1+c2T+c3R+c4TR+c5T2+c6R2+c7T2R+c8TR2+c9T2R2
Heat Index (HI) = 1410.25oF
Therefore, the heat index is 1410.25 Fahrenheit.