Climate Change and the Escalation of Global Extreme Heat: Assessing and Addressing the Risks

The report finds that human-caused climate change significantly increased the frequency and intensity of extreme heat globally from May 2024 to May 2025. Approximately 4 billion people experienced at least 30 additional days of extreme heat, and 195 countries saw the number of such days at least double compared to a world without climate change. All 67 significant heat events analyzed were influenced by climate change, with some becoming dozens of times more likely. The authors emphasize that while adaptation strategies like City Heat Action Plans are vital, comprehensive mitigation through the phasing out of fossil fuels is the only way to limit future harms.

• Between May 1, 2024, and May 1, 2025, human-caused climate change resulted in approximately 4 billion people—roughly 49% of the global population—experiencing at least 30 additional days of extreme heat, defined as temperatures hotter than 90% of local observations from 1991-2020.
• Climate change at least doubled the number of extreme heat days in 195 countries and territories when compared to a counterfactual world without human-induced climate change.
• Aruba recorded the highest number of extreme heat days during the analysis period with 187 days; without human-induced climate change, this number would have been only 45 days.
• All 67 significant extreme heat events identified between May 1, 2024, and May 1, 2025, were influenced by climate change. The event with the strongest influence occurred in the Pacific Islands (May 1-30, 2024), which was made at least 69 times more likely due to climate change.
• Other highly influenced heat events included a period in Central America and northern South America (Aug 30-Sept 4, 2024) made 24 times more likely, a period across central and western Africa (Dec 14-30, 2024) made 15 times more likely, and an event in Saudi Arabia, Kuwait, Iraq, and Bahrain (July 11-16, 2024) made 14 times more likely.
• Heat-related impacts are chronically underreported, especially in low- and middle-income countries, often because deaths are misattributed to comorbid cardiovascular, pulmonary, or renal conditions.
• Vulnerable groups, including older adults, pregnant people, and outdoor workers, face disproportionate risks. Climate change has at least doubled the number of dangerous heat days for pregnant individuals in nearly 90% of countries and territories over the last five years.
• While City Heat Action Plans (HAPs) are used in North America, Europe, Australia, and South Asia, significant gaps in these plans exist in Latin America, the Middle East, Africa, and small island states.

APA

Giguere, Otto, Tannenbaum, & Vahlberg (2025). Climate Change and the Escalation of Global Extreme Heat: Assessing and Addressing the Risks. Climate Central. https://assets.ctfassets.net/cxgxgstp8r5d/4xsn9TLNNtmuTOTzNr2Txl/43dfdaed84074d4e4f481eefff0fbbff/Report__Climate_Change_and_the_Escalation_of_Global_Extreme_Heat__Heat_Action_Day_2025_.pdf

Chicago

Giguere, Otto, Tannenbaum, and Vahlberg. Climate Change and the Escalation of Global Extreme Heat: Assessing and Addressing the Risks. Climate Central, 2025. https://assets.ctfassets.net/cxgxgstp8r5d/4xsn9TLNNtmuTOTzNr2Txl/43dfdaed84074d4e4f481eefff0fbbff/Report__Climate_Change_and_the_Escalation_of_Global_Extreme_Heat__Heat_Action_Day_2025_.pdf.

Wikipedia

{{cite report |last1=Giguere |last2=Otto |last3=Tannenbaum |last4=Vahlberg |title=Climate Change and the Escalation of Global Extreme Heat: Assessing and Addressing the Risks |publisher=Climate Central |date=30 May 2025 |url=https://assets.ctfassets.net/cxgxgstp8r5d/4xsn9TLNNtmuTOTzNr2Txl/43dfdaed84074d4e4f481eefff0fbbff/Report__Climate_Change_and_the_Escalation_of_Global_Extreme_Heat__Heat_Action_Day_2025_.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{giguere2025climate, author = {Giguere and Otto and Tannenbaum and Vahlberg}, title = {{Climate Change and the Escalation of Global Extreme Heat: Assessing and Addressing the Risks}}, institution = {Climate Central}, year = {2025}, month = may, url = {https://assets.ctfassets.net/cxgxgstp8r5d/4xsn9TLNNtmuTOTzNr2Txl/43dfdaed84074d4e4f481eefff0fbbff/Report__Climate_Change_and_the_Escalation_of_Global_Extreme_Heat__Heat_Action_Day_2025_.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }