Editing Extreme weather (section)

===Heat waves===
[[File:Canicule Europe 2003.jpg|thumb|250px|[[2003 European heat wave]]]]
{{ multiple image | total_width=450
| image1 = 1960- Heat wave indicators - US.svg |caption1= US heat waves have increased in frequency, average duration, and intensity.<ref name=EPA_202406/> <br><br>Also, heat wave ''seasons'' have grown in length.<ref name=EPA_202406>{{cite web |title=Climate Change Indicators: Heat Waves |url=https://www.epa.gov/climate-indicators/climate-change-indicators-heat-waves |publisher=U.S. Environmental Protection Agency (EPA) |archive-url=https://web.archive.org/web/20241007114317/https://www.epa.gov/climate-indicators/climate-change-indicators-heat-waves |archive-date=7 October 2024 |date=June 2024 |url-status=live }} EPA cites data source: NOAA, 2024.</ref>
| image2 = 1960- Annual average number of days spent in heat waves - US.svg |caption2= Over decades, the average number of days spent in heat waves in the U.S. annually has increased, based on increases in both the average annual number of heat waves and on their average durations.<ref name=EPA_202406/>
}}
{{Main|Heat wave}}
{{Further|Effects of climate change#Heat waves and temperature extremes}}
{{see|List of heat waves}}
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Heat waves are periods of abnormally high temperatures and [[heat index]]. Definitions of a heatwave vary because of the variation of temperatures in different geographic locations.<ref name="EW">{{cite book|last=Mogil|first=H Michael|title=Extreme Weather|publisher=[[Black Dog & Leventhal Publishers]]|year=2007|isbn=978-1-57912-743-5|location=New York|pages=210–211}}<!--|access-date=2009-08-08--></ref> Excessive heat is often accompanied by high levels of [[humidity]], but can also be catastrophically dry.<ref>{{cite web|author=NOAA NWS|title=Heat: A Major Killer|url=http://nws.noaa.gov/os/heat/index.shtml|archive-url=https://web.archive.org/web/20140705113710/http://www.nws.noaa.gov/os/heat/index.shtml|archive-date=2014-07-05|access-date=2014-06-16}}</ref>

Because heat waves are not visible as other forms of severe weather, like hurricanes, tornadoes, and thunderstorms, they are one of the less known forms of extreme weather.<ref name="heat">{{cite web|author1=Casey Thornbrugh|author2=Asher Ghertner|author3=Shannon McNeeley|author4=Olga Wilhelmi|author5=Robert Harriss|year=2007|title=Heat Wave Awareness Project|url=http://www.isse.ucar.edu/heat/index.html|archive-url=https://web.archive.org/web/20180801235932/http://www.isse.ucar.edu/heat/index.html|archive-date=2018-08-01|access-date=2009-08-18|publisher=[[National Center for Atmospheric Research]]}}</ref> Severely hot weather can damage populations and crops due to potential [[dehydration]] or [[hyperthermia]], [[heat cramps]], [[heat expansion]], and [[heat stroke]]. Dried soils are more susceptible to erosion, decreasing lands available for [[agriculture]]. Outbreaks of wildfires can increase in frequency as dry vegetation has an increased likelihood of igniting. The [[evaporation]] of bodies of water can be devastating to marine populations, decreasing the size of the habitats available as well as the amount of nutrition present within the waters. Livestock and other animal populations may decline as well.

During excessive heat, plants shut their leaf pores ([[stomata]]), a protective mechanism to conserve water but also curtails plants' absorption capabilities. This leaves more pollution and ozone in the air{{cn|date=May 2025}}, which leads to higher mortality in the population{{cn|date=May 2025}}. It has been estimated that extra pollution during the hot summer of 2006 in the UK, cost 460 lives.<ref>{{cite web|year=2013|title=It's not just the heat – it's the ozone: Study highlights hidden dangers|url=http://www.york.ac.uk/news-and-events/news/2013/research/heat-ozone/|publisher=[[University of York]]|access-date=2014-06-16|archive-date=2018-07-29|archive-url=https://web.archive.org/web/20180729060233/https://www.york.ac.uk/news-and-events/news/2013/research/heat-ozone/|url-status=live}}</ref> The European heat waves from summer 2003 are estimated to have caused 30,000 excess deaths, due to heat stress and [[air pollution]].<ref>{{cite journal|last1=Brücker|first1=G.|year=2005|title=Vulnerable populations: Lessons learnt from the summer 2003 heatwaves in europe|journal=Eurosurveillance|volume=10|issue=7|pages=1–2|doi=10.2807/esm.10.07.00551-en|doi-access=free}}</ref> Over 200 U.S cities have registered new record high temperatures.<ref>{{Cite journal|last=Epstein|first=Paul R|date=2005|title=Climate Change and Human Health|journal=The New England Journal of Medicine|volume=353|issue=14|pages=1433–1436|doi=10.1056/nejmp058079|pmc=2636266|pmid=16207843}}</ref> The [[1936 North American heat wave|worst heat wave]] in the US occurred in 1936 and killed more than 5000 people directly. The [[List of disasters in Australia by death toll|worst heat wave]] in Australia occurred in 1938–39 and killed 438. The second worst was in 1896.

Power outages can also occur within areas experiencing heat waves due to the increased demand for electricity (i.e. air conditioning use).<ref>{{cite news|last=Doan|first=Lynn|author2=Covarrubias, Amanda|date=2006-07-27|title=Heat Eases, but Thousands of Southern Californians Still Lack Power|newspaper=[[Los Angeles Times]]|url=http://www.latimes.com/news/local/la-me-heat27jul27,1,4111447.story|access-date=June 16, 2014|archive-date=2023-04-16|archive-url=https://web.archive.org/web/20230416155724/https://www.latimes.com/archives/la-xpm-2006-jul-27-me-heat27-story.html|url-status=live}}</ref> The [[urban heat island]] effect can increase temperatures, particularly overnight.<ref name="Oke">{{cite journal|author=T. R. Oke|year=1982|title=The energetic basis of the urban heat island|journal=Quarterly Journal of the Royal Meteorological Society|volume=108|issue=455|pages=1–24|bibcode=1982QJRMS.108....1O|doi=10.1002/qj.49710845502|s2cid=120122894 }}</ref>