Editing Heat index (section)

==Meteorological considerations==
Outdoors in open conditions, as the relative humidity increases, first haze and ultimately a thicker cloud cover develops, reducing the amount of direct sunlight reaching the surface. Thus, there is an inverse relationship between maximum potential temperature and maximum potential relative humidity. Because of this factor, it was once believed that the highest heat index reading actually attainable anywhere on Earth was approximately {{cvt|71|°C|°F}}. However, in [[Dhahran]], [[Saudi Arabia]] on July 8, 2003, the [[dew point]] was {{cvt|35|°C}} while the temperature was {{cvt|42|°C}}, resulting in a heat index of {{cvt|81|°C}}.<ref>{{Cite news|url=http://www.businessinsider.com/dhahran-saudi-arabia-most-intolerabe-heat-climate-change-2015-10|title=This Saudi city could soon face unprecedented and unlivable heat levels|work=Business Insider|access-date=2017-07-20|language=en}}</ref>  On August 28, 2024, a weather station in southern Iran recorded a heat index of {{cvt|82.2|°C}}, which will be a new record if confirmed.<ref>{{cite|url=https://www.intellinews.com/possible-record-heat-index-of-82-2-c-reported-in-southern-iran-340967/|title=Possible record heat index of 82.2°C reported in southern Iran|author=bne Gulf bureau|date=August 29, 2024}}</ref>

The human body requires evaporative cooling to prevent overheating. [[Wet-bulb temperature]] and [[Wet-bulb globe temperature]] are used to determine the ability of a body to eliminate excess heat.  A sustained wet-bulb temperature of about {{cvt|35|C}} can be fatal to healthy people; at this temperature our bodies switch from shedding heat to the environment, to gaining heat from it.<ref name=pnas>{{cite journal |first1=S.C. |last1=Sherwood |first2=M. |last2=Huber |title=An adaptability limit to climate change due to heat stress |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=107 |issue=21 |pages=9552–5 |date=25 May 2010 |pmid=20439769 |doi=10.1073/pnas.0913352107 |pmc=2906879|bibcode = 2010PNAS..107.9552S |doi-access=free }}</ref> Thus a wet bulb temperature of {{convert|35|C}} is the threshold beyond which the body is no longer able to adequately cool itself.<ref>{{cite journal | url=http://www.gfdl.noaa.gov/news-app/story.77 |first1= John P. |last1=Dunne |first2=Ronald J. |last2=Stouffer |first3=Jasmin G. |last3=John | year=2013 | title= Heat stress reduces labor capacity under climate warming | journal= Nature Climate Change|volume= 3 |issue= 6 |pages= 563 | doi=10.1038/nclimate1827|bibcode = 2013NatCC...3..563D |url-access=subscription }}</ref>