Editing Heat wave (section)

== Impacts on societies ==

=== Reduced economic outputs ===
[[File:09 Aus heatwave map.PNG|thumb|right|2009 southeastern Australia heat wave, thermal map approximate affected area shown in red]]
Calculations from 2022 suggest that heat waves will shrink the global economy by about 1 percent decrease by the middle of the 21st century.<ref>{{Cite web |last=Benedek |first=Réfi |date=2022-07-12 |title=The cost of heatwaves |url=https://hypeandhyper.com/en/the-cost-of-heatwaves/ |access-date=2022-07-15 |publisher=HYPEANDHYPER }}</ref><ref>{{Cite magazine |title=Rising Heat is Making it Harder to Work in the U.S. — the Costs for the Economy Will Soar with Climate Change |url=https://time.com/6093845/how-heat-hurts-the-economy/ |magazine=Time |access-date=2022-07-15}}</ref><ref name=":4"/>

Heat waves often have complex effects on economies. They reduce labour productivity, disrupt agricultural and industrial processes and damage infrastructure that is not suitable for extreme heat.<ref name=":3" /><ref name=":4" /> In 2016, a marine heatwave in Chile and its subsequent [[harmful algal bloom]] caused $800 million (USD) in export losses for the aquaculture industry as salmon and shellfish died off.<ref>{{Cite journal |last1=Trainer |first1=Vera L. |last2=Moore |first2=Stephanie K. |last3=Hallegraeff |first3=Gustaaf |last4=Kudela |first4=Raphael M. |last5=Clement |first5=Alejandro |last6=Mardones |first6=Jorge I. |last7=Cochlan |first7=William P. |date=2020-01-01 |title=Pelagic harmful algal blooms and climate change: Lessons from nature's experiments with extremes |journal=Harmful Algae |series=Climate change and harmful algal blooms |volume=91 |pages=101591 |doi=10.1016/j.hal.2019.03.009 |issn=1568-9883|doi-access=free |pmid=32057339 |bibcode=2020HAlga..9101591T }}</ref>

=== Reduced agricultural outputs ===
{{Main|Effects of climate change on agriculture}}

Heat waves are a big threat to agricultural production. In 2019 heat waves in the [[Mulanje]] region of [[Malawi]] involved temperatures as high as {{cvt|40|°C}}. This and a late rain season scorched tea leaves and reduced yields.<ref>{{Cite web |title=Malawi heatwaves threaten tea yields and livelihoods |publisher=Future Climate Africa |url=https://futureclimateafrica.org/news/malawi-heatwaves-threaten-tea-yields-and-livelihoods/ |access-date=2020-09-24 }}</ref>

==== Farmed animals ====
{{excerpt|Effects of climate change on livestock#Health impacts of heat stress}}

=== Infrastructural damage ===
Heat waves cause roads and highways to buckle and melt,<ref>{{Cite news |date=15 July 2013 |title=When does tarmac melt? |url=https://www.bbc.com/news/magazine-23315384 |publisher=BBC News}}</ref> water lines to burst, and power transformers to detonate, causing fires. A heat wave can also damage railways, by buckling and kinking rails. This can slow down or delay traffic. It can even lead to cancellations of service when rails are too dangerous to traverse by trains.

=== Power outages ===
Heat waves often lead to spikes in electricity demand because there is more use of air conditioning. This can create power outages, making the problem worse. During the [[2006 North American heat wave]], thousands of homes and businesses went without power, especially in California. In Los Angeles, electrical transformers failed, leaving thousands without power for as long as five days.<ref>{{cite news |last=Doan |first=Lynn |author2=Covarrubias, Amanda |date=27 July 2006 |title=Heat Eases, but Thousands of Southern Californians Still Lack Power |url=http://www.latimes.com/news/local/la-me-heat27jul27,1,4111447.story |access-date=16 June 2014 |work=Los Angeles Times}}</ref>
The [[early 2009 southeastern Australia heat wave]] caused major power disruptions in the city of Melbourne. They left over half a million people without power as the heat wave blew transformers and overloaded a power grid.