How much does wind speed affect heat index values? rnThe heat index is really an apparent or effective temperature that indicates how warm you feel under different combinations of temperature and humidity. It is the most common index that the National Weather Service (NWS) uses to measure discomfort during sultry conditions. The concept of a heat index was originally developed and first published by R.G. Steadman in a 1979 issue of the journal of Applied Meteorology. His original tables-including one that gives the heat index as a function of temperature and dewpoint-are still considered a standard. Several empirical formulas have been developed that reproduce the values in that table fairly well, but one in particular, a formula proposed by Carl Schoen in 2005 (again in the Journal of Applied Meteorology), is now preferred. Schoen's formula is favored for its simplicity, accuracy, and helpful extrapolation when the input values of temperature and dewpoint lie outside the range considered in Steadman's table.
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