Estimate apparent temperature and heat-stress risk from weather conditions.
Overview
Heat index estimates how hot conditions feel by combining air temperature with relative humidity.
High humidity impairs sweat evaporation, reducing cooling and increasing risk of heat illness during exercise or work.
Steps
Use shaded ambient temperature in degrees Fahrenheit.
Use weather-station humidity percentage.
Calculator computes apparent temperature.
Compare output to caution, extreme caution, danger bands.
Reduce intensity, add cooling breaks, increase hydration.
Stop activity with cramps, dizziness, or confusion.
Math
HI = -42.379 + 2.04901523T + 10.14333127RH - 0.22475541TRH - 6.83783e-3T^2 - 5.481717e-2RH^2 + 1.22874e-3T^2RH + 8.5282e-4TRH^2 - 1.99e-6T^2RH^2
The Rothfusz regression estimates apparent temperature (HI) from air temperature T (degrees F) and relative humidity RH (%).
Worked cases
Apply Rothfusz equation
Heat index is about 106 F (dangerous exertion conditions)
Apply equation with low RH
Heat index remains closer to air temperature than humid case
Heat index ~100 F
Move hard intervals earlier and increase fluid/electrolyte strategy
Why use this
Questions