Today's Heat Waves Feel a Lot Hotter Than Heat Index Implies

hubie writes:

Today's heat waves feel a lot hotter than heat index implies:

If you looked at the heat index during this summer's sticky heat waves and thought, "It sure feels hotter!," you may be right.

An analysis by climate scientists at the University of California, Berkeley, finds that the apparent temperature, or heat index, calculated by meteorologists and the National Weather Service (NWS) to indicate how hot it feels - taking into account the humidity - underestimates the perceived temperature for the most sweltering days we're now experiencing, sometimes by more than 20 degrees Fahrenheit.

[...] The finding has implications for those who suffer through these heat waves, since the heat index is a measure of how the body deals with heat when the humidity is high, and sweating becomes less effective at cooling us down. Sweating and flushing, where blood is diverted to capillaries close to the skin to dissipate heat, plus shedding clothes, are the main ways humans adapt to hot temperatures.

[...] The heat index was devised in 1979 by a textile physicist, Robert Steadman, who created simple equations to calculate what he called the relative "sultriness" of warm and humid, as well as hot and arid, conditions during the summer. He saw it as a complement to the wind chill factor commonly used in the winter to estimate how cold it feels.

His model took into account how humans regulate their internal temperature to achieve thermal comfort under different external conditions of temperature and humidity - by consciously changing the thickness of clothing or unconsciously adjusting respiration, perspiration and blood flow from the body's core to the skin.

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