Why/how can the heat index be lower than the temperature?

Question

Why/how can the heat index be lower than the temperature?

Answer 1

I will give you a correct answer.  The heat index involves a mathematical equation between the air temp and relative humidity to determine on how it feels on the human body.  It has nothing to do with wind speed and can in fact be lower than the  air temp.  The locations where this would happen would be like in Arizona or anywhere that experiences  "dry heat" where the humidity and dew point is low.  The formula below is used to calculate the heat index I put it below for fun to show you.

    HI = c_1 + c_2 T + c_3 R + c_4 T R + c_5 T^2 + c_6 R^2 + c_7 T^2R + c_8 T R^2 + c_9 T^2 R^2\ \,

Answer 2

The Late Show with David Letterman discussed this last or the night before last night, it makes absolutely no sense =P

Answer 3

Temperature considers only . . .temperature.

heat index also considers humidity, wind, and some other environmental factors. A strong wind with no humidity makes a hot day feel cooler than the same temperature with high humidity and no wind.

"heat Index" is the heat equivalent of "wind chill factor" on cold days.