Extreme heat is becoming more frequent, intense and prolonged as climate change raises temperatures around the world, according to the World Meteorological Organization. Europe is enduring its fifth heatwave of the summer, while large parts of the United States have experienced dangerous temperatures in the 90s and triple digits.
The human toll is mounting. The World Health Organization reported more than 1,300 excess deaths during Europe’s first major heatwave this summer. A later WHO assessment estimated approximately 10,650 excess deaths during one week in June, although excess-death figures include fatalities that cannot all be directly attributed to heat.
In the United States, heat-related mortality has risen sharply. A JAMA study led by UT San Antonio public health professor Jeffrey Howard identified 21,518 heat-related deaths from 1999 through 2023. Annual deaths increased from 1,069 to 2,325 during that period. Howard cautions that part of the increase could reflect better reporting, but death certificates frequently fail to identify heat as a contributing factor, suggesting the actual toll may be higher.
Emerging research also indicates that prolonged heat exposure may accelerate biological aging. A 2025 study in Science Advances found that older Americans living in areas with more extremely hot days showed faster epigenetic aging.
The danger is often greatest in low-income neighborhoods with limited tree cover, aging homes and inadequate air conditioning. UT San Antonio researchers mapped San Antonio’s most heat-vulnerable neighborhoods and placed sensors in Historic Westside homes, where professor Esteban López Ochoa said interior temperatures can reach 120 degrees.
Researchers created digital replicas of 10 homes to test how affordable repairs could improve indoor conditions. The work helped a neighborhood community land trust secure nearly $200,000 for repairs. The program is now expanding as San Antonio considers targeted investments in weatherization, trees and heat-reflective pavement.
Guests:
Jeffrey Howard, Ph.D. is an Associate Professor of Public Health at the University of Texas at San Antonio.
Kristen E. Brown, Ph.D, is an Assistant Professor of Environmental Engineering in the Klesse College of Engineering and Integrated Design at the University of Texas at San Antonio.
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This interview will be recorded live on Wednesday August 12, 2026, at 12:00 p.m.
