Recently, many have mentioned the concept of the heat index, a measure of how hot the air feels based on temperature and humidity. This index often presents a number higher than the actual temperature. For instance, while the temperature in Central Park might be 98 degrees, the heat index can be 105. Essentially, higher humidity makes it feel hotter because moisture in the air reduces perspiration evaporation from your skin.
What exactly is the heat index, and how was it developed?
At its core, the heat index is a complex calculation that expands on the saying, “it’s not the heat, it’s the humidity.” The formula considers both temperature (T) and relative humidity (H), expressed as:
Heat Index = (T × 2.049) + (H × 10.143) – (T × H × 0.225) – (T² × 0.007) – (H² × 0.055) + (T² × H × 0.001) + (H² × T × 0.001) – (T² × H² × 0.000002) – 42.379.
This formula was created by Lans Rothfusz, a former meteorologist with the National Weather Service. He developed this equation in 1990 while working as an intern at the Weather Service’s Southern Region Headquarters in Fort Worth. Rothfusz’s work earned him recognition, including the National Weather Association’s 2014 operational achievement award.