Editing Heat index (section)

== History ==
The heat index was developed in 1979 by [[Robert G. Steadman]].<ref name=SteadmanI>{{cite journal|last1=Steadman|first1=R. G.|title=The Assessment of Sultriness. Part I: A Temperature-Humidity Index Based on Human Physiology and Clothing Science|journal=Journal of Applied Meteorology|date=July 1979|volume=18|issue=7|pages=861–873|doi=10.1175/1520-0450(1979)018<0861:TAOSPI>2.0.CO;2|bibcode=1979JApMe..18..861S|doi-access=free}}</ref><ref>{{cite journal|last1=Steadman|first1=R. G.|title=The Assessment of Sultriness. Part II: Effects of Wind, Extra Radiation and Barometric Pressure on Apparent Temperature|journal=Journal of Applied Meteorology|date=July 1979|volume=18|issue=7|pages=874–885|doi=10.1175/1520-0450(1979)018<0874:TAOSPI>2.0.CO;2|bibcode=1979JApMe..18..874S|doi-access=free}}</ref> Like the [[wind chill]] index, the heat index contains assumptions about the human body mass and height, clothing, amount of physical activity, individual heat tolerance, sunlight and ultraviolet radiation exposure, and the wind speed. Significant deviations from these will result in heat index values which do not accurately reflect the perceived temperature.<ref>{{Cite web |url=http://www.slate.com/id/2123486/fr/rss/ |title=How do they figure the heat index? - By Daniel Engber - Slate Magazine<!-- Bot generated title --> |access-date=2008-02-01 |archive-date=2011-06-21 |archive-url=https://web.archive.org/web/20110621004825/http://www.slate.com/id/2123486/fr/rss |url-status=dead }}</ref>

In [[Canada]], the similar [[humidex]] (a Canadian innovation introduced in 1965)<ref>"Spring and Summer Hazards". Environment and Climate Changes. Government of Canada. Retrieved 2016-09-22.</ref> is used in place of the heat index. While both the humidex and the heat index are calculated using dew point, the humidex uses a dew point of {{convert|7|°C}} as a base, whereas the heat index uses a dew point base of {{convert|14|°C}}.{{explain|reason= doesn't the heat index simply use relative humidity?|date=November 2022}} Further, the heat index uses heat balance equations which account for many variables other than vapor pressure, which is used exclusively in the humidex calculation. A joint committee{{Who|date=October 2015}} formed by the United States and Canada to resolve differences has since been disbanded.{{citation needed|date=October 2015}}