What exactly is extreme heat? The phrase generally describes temperatures well above normal for a given place.
Heatwaves are one manifestation of extreme heat. What constitutes a heatwave depends on local climate conditions and how people, infrastructure and ecosystems are adapted to them.
A heatwave is not simply a sequence of hot days. A defining characteristic is the build-up of excess heat over successive days and nights. During normal conditions, cooler nights allow people, buildings and the environment to release heat absorbed during the day. When nights remain unusually warm, this recovery process is disrupted and less of that heat is dissipated. As heat intensifies, pressure on energy and transport systems grows, vegetation dries out, wildfire risk rises and crops, plants and animal species face increasing stress.
Source: https://wmo.int/topics/extreme-heat
UN Entities
- Secretary-General’s Call to Action on Extreme Heat
https://www.un.org/en/climatechange/extreme-heat - Global Heat Health Information Network
https://ghhin.org/
The Global Heat Health Information Network is a dynamic voluntary community of policymakers, scientists, practitioners, working together for a world where extreme heat is no barrier to lives and livelihoods. The Network is an initiative of WMO, WHO, and NOAA. Its Technical Support Unit (TSU), hosted at the World Meteorological Organization in Geneva, provides global coordination and management. - Food and Agriculture Organization of the United Nations (FAO)
- The heat is on: Four examples of practical solutions to extreme heat in agriculture (22 April 2026): https://www.fao.org/newsroom/story/the-heat-is-on/en
- Don’t sweat it… or do! Three things to know about heat stress and how to prevent it (3 September 2025): https://www.fao.org/newsroom/story/don-t-sweat-it-or-do!/en
- International Labour Organization (ILO)
- Recommendations for health and safety amidst heatwaves: https://www.ilo.org/resource/news/recommendations-health-and-safety-amidst-heatwaves
- Podcast – Heat: a silent killer at work (5 June 2025): https://voices.ilo.org/podcast/heat-a-silent-killer-at-work
- United Nations Human Settlements Programme (UN-Habitat)
- Eleni Myrivili’s passionate pursuit: A Chief Heat Officer on a mission: https://unhabitat.org/eleni-myrivilis-passionate-pursuit-a-chief-heat-officer-on-a-mission
- United Nations Development Programme (UNDP)
- Beat the Heat: All hands-on deck for Our City-Our Action campaign against heatwaves! https://www.sparkblue.org/basic-page/heatwave-resilience
- United Nations Office for Disaster Risk Reduction (UNDRR)
- Extreme Heat Portal: https://www.preventionweb.net/hubs/extreme-heat
- Heat risk assessment: https://www.preventionweb.net/collections/heat-risk-assessment
- Chronic heat: impacts and solutions from South-East Asia and East Africa (22 June 2026): https://www.undrr.org/news/chronic-heat-impacts-and-solutions-south-east-asia-and-east-africa
- Understanding the trends of heat risk (8 May 2026): https://www.undrr.org/news/understanding-trends-heat-risk
- Rethinking how buildings can adapt to extreme heat (8 May 2026): https://www.undrr.org/news/rethinking-how-buildings-can-adapt-extreme-heat
- The hidden links between heat, water, and energy (8 May 2026): https://www.undrr.org/news/hidden-links-between-heat-water-and-energy
- The silent killer: We need better risk governance to beat extreme heat (11 June 2025): https://www.undrr.org/news/silent-killer-we-need-better-risk-governance-beat-extreme-heat-gp-2025
- United Nations Environment Programme (UNEP)
- 50 cities at 50º Celsius: Too hot to ignore. Too urgent to delay: https://coolcoalition.org/media-center/campaigns/50-50
- 50 Cities for climate action: avoiding and adapting to a 50°C world (2 June 2026): https://www.unep.org/news-and-stories/press-release/50-cities-climate-action-avoiding-and-adapting-50degc-world
- Nine ways to stay cool during a heatwave (22 June 2026): https://www.unep.org/news-and-stories/story/nine-ways-stay-cool-during-heatwave
- As the planet swelters, World Environment Day 2026 focuses on urgent climate action (5 June 2026): https://www.unep.org/news-and-stories/press-release/planet-swelters-world-environment-day-2026-focuses-urgent-climate
- Boiling hot: how countries can beat the growing threat of extreme heat (25 July 2025): https://www.unep.org/news-and-stories/story/boiling-hot-how-countires-can-beat-growing-threat-extreme-heat
- As heat records fall, experts call for reductions in this often-overlooked greenhouse gas (16 January 2025): https://www.unep.org/news-and-stories/story/heat-records-fall-experts-call-reductions-often-overlooked-greenhouse-gas
- Five ways cities can keep it chill while cutting emissions (5 December 2023): https://www.unep.org/news-and-stories/story/five-ways-cities-can-keep-it-chill-while-cutting-emissions
- As heatwaves blanket Europe, cities turn to nature for solutions (29 July 2022): https://www.unep.org/news-and-stories/story/heatwaves-blanket-europe-cities-turn-nature-solutions
- 50 cities at 50º Celsius: Too hot to ignore. Too urgent to delay: https://coolcoalition.org/media-center/campaigns/50-50
- United Nations Children’s Fund (UNICEF)
- Explainer – Heat waves and how they impact children: https://www.unicef.org/stories/heat-waves-impact-children
- Explainer – Heat wave safety tips: https://www.unicef.org/parenting/emergencies/heat-wave-safety-tips
- United Nations University – Institute for Environment and Human Security (UNU-EHS)
- 5 Facts on Marine Heatwaves: Heatwaves exist not only on land, but also in oceans (6 June 2025): https://unu.edu/ehs/article/5-facts-marine-heatwaves
- 5 Critical Observations on Unbearable Heat and Human Health: The increase in global temperatures poses severe risks to human health (3 April 2024): https://unu.edu/ehs/series/5-critical-observations-unbearable-heat-and-human-health
- Record-breaking Heat: 5 Facts on Rising Temperatures: Five facts on record-breaking heat and rising temperatures (12 July 2023): https://unu.edu/ehs/series/record-breaking-heat-5-facts-rising-temperatures
- World Health Organization (WHO)
- Heatwaves: https://www.who.int/health-topics/heatwaves
- Beat the Heat: Tips for keeping cool: https://www.who.int/initiatives/initiative-against-extreme-heat-and-health-risks-in-workplaces-and-major-events/tips-for-keeping-cool
- World Health Organization (WHO/Europe)
- Heatwaves: https://www.who.int/europe/health-topics/heatwaves
- Heat Action Day: New WHO guidance helps authorities better protect people from the effects of heat (11 June 2026): https://www.who.int/europe/news/item/11-06-2026-heat-action-day–new-who-guidance-helps-authorities-better-protect-people-from-the-effects-of-heat
- Strengthening heat–health action plans to protect public health, with WHO guidance (2 June 2026): https://www.who.int/europe/news/item/02-06-2026-strengthening-heat-health-action-plans-to-protect-public-health–with-who-guidance
- WHO/Europe annual #KeepCool campaign: https://www.who.int/europe/news/item/23-06-2025-how-summer-heat-impacts-health-and-how-to–keepcool
- World Meteorological Organization (WMO)
- Extreme Heat: https://wmo.int/topics/extreme-heat
- Records fall as extreme heat grips Europe (26 June 2026): https://wmo.int/media/news/records-fall-extreme-heat-grips-europe
- New report suggests more global temperature records ahead (28 May 2026): https://wmo.int/news/media-centre/new-report-suggests-more-global-temperature-records-ahead
- WMO opens UNGA activity with early warnings and extreme heat solutions dialogue (22 September 2025): https://wmo.int/media/news/wmo-opens-unga-activity-early-warnings-and-extreme-heat-solutions-dialogue
- Extreme heat impacts millions of people (7 August 2025): https://wmo.int/media/news/extreme-heat-impacts-millions-of-people
- Heatwaves and wildfires coincide with anniversary of Call to Action on Extreme Heat (28 July 2025): https://wmo.int/media/news/heatwaves-and-wildfires-coincide-anniversary-of-call-action-extreme-heatf
- Extreme heat grips Europe (3 July 2025): https://wmo.int/media/news/extreme-heat-grips-europe
Selected Statements and Speeches by UN Officials
- Europe lost 200 000 people to heat in 4 years yet nearly all of them were preventable – Statement by Dr Hans Henri P. Kluge, WHO Regional Director for Europe, at the launch of WHO’s new guidance to protect lives from extreme heat (11 June 2026): https://www.who.int/europe/news/item/11-06-2026-statement—europe-lost-200-000-people-to-heat-in-4-years-yet-nearly-all-of-them-were-preventable
- One year on: Collective action where the heat hits hardest / Op Ed by Kamal Kishore, Special Representative of the United Nations Secretary-General for Disaster Risk Reduction, 25 July 2025: https://www.undrr.org/news/one-year-collective-action-where-heat-hits-hardest
- The climate crisis is a health crisis – and the European Region is in the hot seat / Opening remarks by Dr Hans Henri P. Kluge, WHO Regional Director for Europe, at the launch and first hearing of the Pan-European Commission on Climate and Health, Reykjavík, Iceland, 11 June 2025: https://www.who.int/europe/news/item/11-06-2025-statement-the-climate-crisis-is-a-health-crisis-and-the-european-region-is-in-the-hot-seat
- Celeste Saulo, WMO Secretary-General, Opening Remarks during the Special Event on Extreme Heat Risk Governanace, 5 June 2025: https://wmo.int/content/opening-remarks-during-special-event-extreme-heat-risk-governanace
- Following hottest year on record, Secretary-General says scaling up renewable power, adaptation key for restoring good health to Mother Earth, in observance message (SG/SM/22623, 14 April 2025): https://press.un.org/en/2025/sgsm22623.doc.htm
- 2024 hottest year on record, Secretary-General warns, urging trailblazing climate action in 2025 to limit global temperature rise to 1.5°C, support most vulnerable (SG/SM/22517, 10 January 2025): https://press.un.org/en/2025/sgsm22517.doc.htm
- Early warning systems, protection from extreme heat ‘are not luxuries’, Secretary-General tells event at Baku Climate Change Conference (SG/SM/22452, 13 November 2024): https://press.un.org/en/2024/sgsm22452.doc.htm
- Celeste Saulo, WMO Secretary-General, Statement on the occasion of the high-level event on Delivering Early Warnings for All and Addressing Extreme Heat, 13 November 2024: https://wmo.int/content/statement-occasion-of-high-level-event-delivering-early-warnings-all-and-addressing-extreme-heat
- Ten actions to combat extreme heat / Op Ed by Kamal Kishore, Special Representative of the United Nations Secretary-General for Disaster Risk Reduction (12 November 2024): https://www.undrr.org/news/ten-actions-combat-extreme-heat
- Humanity paying price for torching planet, Secretary-General says at UN Environment Programme Adaptation Gap Report launch, urging action to address climate calamity (SG/SM/22443, 7 November 2024): https://press.un.org/en/2024/sgsm22443.doc.htm
- Heat claims more than 175 000 lives annually in the WHO European Region, with numbers set to soar / Statement by the WHO Regional Director for Europe, Dr Hans Henri P. Kluge, 1 August 2024: https://www.who.int/europe/news/item/01-08-2024-statement–heat-claims-more-than-175-000-lives-annually-in-the-who-european-region–with-numbers-set-to-soar
- Following three hottest days on record, Secretary-General launches global action call to care for most vulnerable, protect workers, boost resilience using data, science (SG/SM/22319, 25 July 2024): https://press.un.org/en/2024/sgsm22319.doc.htm
- Climate breakdown has begun with hottest summer on record, Secretary-General warns, calling on leaders to ‘turn up the heat now’ for climate solutions (SG/SM/21926, 6 September 2023): https://press.un.org/en/2023/sgsm21926.doc.htm
Selected UN Publications & Documents
- Heat–Health Action Plans: Guidance; Second edition (WHO/Europe, June 2026): https://www.who.int/europe/publications/i/item/9789289062930
- Global Annual to Decadal Climate Update 2026-2035 (WMO, May 2026):
- One-Fifth of the World’s Population Is at High Risk of Climate-Related Hazards (World Bank Policy Research Working Paper 11380, May 2026): https://hdl.handle.net/10986/44886
- Rising Heat in the Labor Market: The Impact of Rising Temperatures on Firms and Jobs in Europe (World Bank Policy Research Working Paper 11375, May 2026): https://hdl.handle.net/10986/44828
- Gender-differentiated and age-specific risks of heat stress in a warming world: Implications for equality and resilience (UN Women, April 2026): https://tinyurl.com/5ayxmtr7
- Extreme heat and agriculture: FAO–WMO joint report (April 2026): https://doi.org/10.4060/cd9394en
- Flames of change: Children and youth at the forefront of tackling urban heat (UNDRR, March 2026): https://www.undrr.org/publication/documents-and-publications/flames-change-children-and-youth-forefront-tackling-urban
- Rising temperatures, rising tensions: The urban climate-conflict nexus amid the global housing crisis (UN Habitat, 2025): https://unhabitat.org/rising-temperatures-rising-tensions-the-urban-climate-conflict-nexus-amid-the-global-housing-crisis
- Rising heat, rising risk: policy pathways for regional resilience (ESCAP, November 2025): https://hdl.handle.net/20.500.12870/8516
- Extreme Heat Risk Governance Toolkit and Framework (UNDRR, November 2025): https://www.undrr.org/publication/documents-and-publications/extreme-heat-risk-governance-toolkit-and-framework
- Disaster Resilience Scorecard for Cities: Addendum for Extreme Heat Risk Management (UNDRR, November 2025): https://mcr2030.undrr.org/extreme-heat-scorecard
- Flames of change II: Urban action on extreme heat across Europe and Central Asia (UNDRR, October 2025): https://www.undrr.org/publication/flames-change-ii-urban-action-extreme-heat-across-europe-and-asia
- Unlivable: Confronting Extreme Urban Heat in Latin America and the Caribbean (World Bank, September 2025): https://hdl.handle.net/10986/43751
- Heatwaves and Their Effects on Transportation Systems: A Comprehensive Review (World Bank, September 2025): https://hdl.handle.net/10986/43727
- Handbook on Urban Heat Management in the Global South (World Bank, September 2025): https://hdl.handle.net/10986/43654
- Climate change and workplace heat stress: technical report and guidance (WMO / WHO, August 2025): https://www.who.int/publications/i/item/9789240099814
- Narrative analysis: Case studies in heat resilience (GHHIN, July 2025): https://www.undrr.org/publication/documents-and-publications/narrative-analysis-case-studies-heat-resilience
- An assessment of heat action plans: Global standards, good practices and partnerships (GHHIN, July 2025): https://www.preventionweb.net/publication/documents-and-publications/assessment-heat-action-plans-global-standards-good-practices
- Stocktake report: Heat action across United Nations Entities and International Organizations (GHHIN, July 2025): https://www.preventionweb.net/publication/documents-and-publications/stocktake-report-heat-action-across-united-nations-entities
- Frontiers 2025: The Weight of Time – Facing a new age of challenges for people and ecosystems (UNEP, July 2025): https://www.unep.org/resources/frontiers-2025-weight-time
- Unlivable. How Cities in Europe and Central Asia Can Survive ‒ and Thrive ‒ in a Hotter Future (World Bank, June 2025): https://hdl.handle.net/10986/43344
- Health advice for hot weather (WHO Advocacy brief, May 2025): https://www.who.int/europe/publications/m/item/health-advice-for-hot-weather
- Cooling and Extreme Heat Factsheet (UNEP Factsheet, January 2025): https://www.unep.org/resources/factsheet/cooling-and-extreme-heat-factsheet
- E/C.16/2025/7 (27 January 2025): Effective governance for extreme heat: integrating institutional frameworks with the energy shift: note / by the Secretariat: https://docs.un.org/E/C.16/2025/7
- Extreme heat risk reduction: Towards a common global framework (WMO / UNDRR, 2025): https://www.undrr.org/publication/extreme-heat-risk-reduction-towards-common-global-framework
- Urban Extreme Heat Risk Management: Resource Package (UNDRR, 2025): https://www.undrr.org/publication/urban-heat-risk-management-resource-package
- Combating Heat in Cities: Operationalizing the Urban Heat Agenda at the World Bank (October 2025): https://hdl.handle.net/10986/42303
- Heat at work: Implications for safety and health; A global review of the science, policy and practice (ILO, July 2024): https://www.ilo.org/publications/heat-work-implications-safety-and-health
- Beat the heat: Child health amid heatwaves in Europe and Central Asia; Policy Brief (UNICEF, July 2024): https://www.unicef.org/eca/reports/beat-heat-2024
- Analysis of heat waves and urban heat island effects in central European cities and implications for urban planning (World Bank / GFDRR / ZAMG, 2024): https://www.preventionweb.net/publication/analysis-heat-waves-and-urban-heat-island-effects-central-european-cities-and
- Global Cooling Watch 2023 – Keeping it Chill: How to meet cooling demands while cutting emissions (UNEP, December 2023): https://www.unep.org/resources/global-cooling-watch-2023
- The coldest year of the rest of their lives: Protecting children from the escalating impacts of heatwaves (UNICEF, October 2022): https://uni.cf/3Up3L1x
- Extreme Heat: Preparing for the heatwaves of the future (OCHA / IFRC, October 2022): https://www.preventionweb.net/publication/extreme-heat-preparing-heatwaves-future
- Beating the Heat: A Sustainable Cooling Handbook for Cities (UNEP, November 2021): https://www.unep.org/resources/report/beating-heat-sustainable-cooling-handbook-cities
- Emissions Gap Report 2021: the heat is on – a world of climate promises not yet delivered (UNEP, October 2021): https://www.unep.org/resources/emissions-gap-report-2021
26 June 2026
not an official document – for information only
https://unric.org/en/unric-library-backgrounder-extreme-heat/