Heat index explainer

WTHI (Terre Haute) - See video on left side of your screen for a demonstration.

The heat index combines air temperature and humidity. This gives us the "feels-like" temperature.

Sweating is how our bodies cool off. The sweat evaporates and carries heat away from the body. When the humidity is high, the evaporation rate is reduced. The body keeps more heat than it would in dry air.

For a given temperature and humidity level, that is how a person feels. Measurements have been taken based off those descriptions. This is where our heat index is derived from, relating to one temperature and humidity combination to another at a higher temperature in drier air.