Early on the evening of August 22, 2024, Jeff Howard was preparing dinner in his northeast San Antonio home while the local TV news played quietly in the background.
“A developing story now. Police find a homeless woman dead on the sidewalk,” the news anchor said.
At this, Howard dropped what he was doing and hurried closer to the TV.
“The cause is believed to be from the extreme heat.”
Howard knew that was likely because a high-pressure system known as a heat dome had recently moved over South Texas. The meteorological phenomenon acts like a closed oven door, trapping a roiling mass of hot air below. The official temperature that day had reached 106 degrees Fahrenheit (41°C) – 12 degrees higher than average for that date. The dead woman was later identified as 46-year-old Jessica Witzel.
Although Howard didn’t know her, Witzel’s death hit him hard.
“It was right here in San Antonio,” he said. “A specific person gives the numbers a name and a face.”
A tragic example of a growing trend
Howard is a numbers guy by profession. An associate professor of public health at the University of Texas at San Antonio – a 15-minute drive from where Witzel died – Howard specializes in using large data sets to understand acute and long-term health consequences from exposure to traumas of all sorts.
Heat-related deaths were already uppermost on his mind that evening. He was the lead author of a study about to be published in the Journal of the American Medical Association. “Trends of Heat-Related Deaths in the US, 1999–2023” was the first scientific paper to document an abrupt, steep rise in heat-related deaths across the country, one that is likely linked to climate change.
The study found that between 1999 and 2023, the heat-related mortality rate – the number of deaths per 100,000 people – rose by 63%. But the data showed something even more disturbing: The trend is rapidly accelerating.
“The death rate,” Howard said, “has risen 117% in the last seven years.”
Sara Meerow is an urban heat expert at Arizona State University in Tempe, a city just to the east of Phoenix in Maricopa County. Last year, 645 heat-related deaths were recorded in the county. Heat deaths have long been considered a problem largely confined to the Phoenix metro area, Meerow said.
But Howard’s research “suggests that increases in the number of heat-related deaths over the past few years in Phoenix, Arizona, are part of a national trend,” she said.
Meerow, an associate professor in the School of Geographical Sciences and Urban Planning at ASU, was herself the lead author of a journal article published only days before Howard’s. Hers looked at what officials are doing – and failing to do – to reduce heat-related deaths in the U.S.
Heat waves expose gaps in protecting vulnerable communities
Although heat kills more U.S. residents than any other form of extreme weather, Meerow pointed out that “compared with other hazards like flooding, heat is less visible and largely unregulated.”
For example, Meerow noted in the paper, the federal government maps flood zones, builds levees, subsidizes flood insurance, and provides financial and other aid to people who have suffered a flooding disaster. But there are no similar measures to help U.S. residents likely to experience deadly heat waves.
Jessica Witzel’s death is a tragically typical example of how officials at all levels of government are failing to protect Americans from extreme heat.
Witzel was unhoused and had been diagnosed with severe mental disorders. Living on the street, without access to a cool shelter, people are far more likely to suffer heat-related illnesses, from temporary heat cramps to potentially lethal heat stroke. Mental disorders can interfere with a person’s ability to recognize when their body temperature is rising to dangerous levels. In rural and urban America, there is a chronic shortage of shelter beds for unhoused people, air-conditioned spaces that are open to the public when needed, and mental health care for vulnerable populations that can’t afford health insurance.
Read: For unhoused people in America’s hottest large city, heat waves are a merciless killer
Witzel died at what could be considered ground zero in San Antonio’s urban heat island, where the combination of vast stretches of concrete and lack of vegetation and shade sends already high temperatures skyrocketing. Waste heat from gas-powered vehicles is a significant contributor to urban heat islands, and Interstate 10 is less than 1,000 feet south of where Witzel was found. To the north, and even closer, is an enormous concrete parking lot servicing the city’s 500-bus transit system.
Exactly how hot it was at the time and place Witzel was found isn’t known, but Greg Harman has a pretty good idea. Harman is the founder of Deceleration, a nonprofit online journal in San Antonio that describes its beat as “the intersection of environment and justice.” During the scorching San Antonio summers, Harman travels to different neighborhoods to document and write about the disparate impact of heat on residents based on location.
The day before Witzel died, Harman had used an extremely accurate tool to measure the temperature and humidity in downtown San Antonio. The official high that day was 108 degrees (42°C), but that reading was taken at the airport, several miles from the city’s hotter urban core.
“Downtown, the air temperature was 119 degrees [48°C],” Harman said. “The heat index, which combines heat and humidity to determine how hot it feels to the human body, was 129 degrees [54°C].”
The hidden toll of underreported heat-related deaths
Witzel’s death also underscores what experts agree is a fundamental problem in working to reduce heat mortalities.
“We’ve known for decades that the official numbers of heat-related deaths are massive underestimates,” said Kristie Ebi, professor of global health at the University of Washington. Without knowing the true size and other details of the problem, she added, it’s hard to set priorities for action.
Ebi pointed to several factors that lead to these undercounts, beginning with the fact that there is no nationwide standard for reporting heat deaths. Bexar County, Texas, for example, which includes San Antonio, doesn’t track deaths caused by heat, which means that Witzel is unlikely to be included in state or national counts of heat mortalities, regardless of what cause of death is listed on her death certificate.
Which points to another problem: Death certificates are not necessarily reliable indicators of heat deaths.
“Extreme heat can cause a heart attack,” Ebi explained. “If somebody comes into an emergency room having a heart attack, the people working there may not know whether the person had been exposed to extreme heat.”
If the patient dies, the cause of death is recorded simply as a heart attack.
Another reason a death certificate may not mention heat is that there’s no state or federal standard for who can issue death certificates.
Read: Climate change played a role in killing tens of thousands of people in 2023
In Texas, large metropolitan areas are likely to have professional medical examiners. “But in smaller cities and in rural areas,” Howard said, “the person filling out the death certificate might be a justice of the peace who has no medical training at all.”
That may partly explain why metro Phoenix reports such a disproportionately large share of heat deaths (in addition to its being a sprawling, car-centric desert city).
“The medical examiner’s office in Phoenix has a rigorous protocol in place for determining heat-related deaths,” Howard said.
Simply put, if you’re actively looking for heat-related deaths, you’ll likely get a more accurate count than if you’re not looking. Given the precipitous rise in heat deaths across the country documented in Howard’s study, he believes getting a more accurate count is vital to taking action to save lives.
“Going forward,” Howard said, “there should be a much more concerted effort nationally around developing protocols and processes that are more standardized for assessing heat-related deaths.”
At a vigil for Jessica Witzel held days after her death, one of her childhood friends put it succinctly. Standing under an umbrella against the intense Texas sunlight, Marisol Cortez, who also co-edits Deceleration, spoke to the small group of family and friends gathered near the spot where Witzel had died.
She directed these words to government officials.
“Count the bodies!” Witzel’s friend demanded.
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