Risky summer heat 2025

Climate Central's analysis for June to August 2025 reveals that at least 22% of the global population experienced temperatures made at least twice as likely by climate change daily. In the U.S., over 21 million people in 32 cities faced 30 or more 'risky heat' days added by climate change, with some cities, such as Honolulu, seeing all their risky heat days attributed to human-caused warming.

• Between June 1 and August 31, 2025, at least 1.8 billion people, or 22% of the global population, experienced daily average temperatures that were at least twice as likely because of climate change (CSI level 2 or higher) every single day.
• In the U.S., the average person experienced approximately 21 days with a strong climate change influence (CSI 2 or higher) during the meteorological summer. In Hawaii, this influence was present nearly every day, totaling 90 out of 92 days.
• More than 21 million people across 32 U.S. cities experienced 30 or more 'risky heat' days—defined as temperatures hotter than 90% of those recorded locally from 1991-2020—that were added by climate change. The highest number of added risky heat days occurred in West Palm Beach, Florida (49), Anchorage, Alaska (48), Miami, Florida (47), and San Juan, Puerto Rico (46).
• Climate change was the sole driver of all risky heat days experienced this summer in several U.S. cities, including Honolulu, Hawaii (38 days), McAllen, Texas (24), Houston, Texas (21), and Waco, Texas (9). In 112 U.S. cities, climate change was responsible for at least half of the risky heat days.
• The U.S. was approximately 0.6°F warmer than the 1991-2020 average from June to August 2025, with 111 out of 247 U.S. cities seeing temperatures at least 1°F warmer than normal.

APA

Climate Central (2025). Risky summer heat 2025. https://www.climatecentral.org/climate-matters/risky-summer-heat-2025

Chicago

Climate Central. Risky summer heat 2025. 2025. https://www.climatecentral.org/climate-matters/risky-summer-heat-2025.

Wikipedia

{{cite report |author=Climate Central |title=Risky summer heat 2025 |date=16 September 2025 |url=https://www.climatecentral.org/climate-matters/risky-summer-heat-2025 |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{climatecentral2025risky, author = {{Climate Central}}, title = {{Risky summer heat 2025}}, institution = {Climate Central}, year = {2025}, month = sep, url = {https://www.climatecentral.org/climate-matters/risky-summer-heat-2025}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }