Adam Willson died in June 2024 in a sweltering house in Tucson, Arizona, and his death certificate says only “Unknown natural causes.” His mother, Debbie Willson, says she knows heat killed him. That gap between lived reality and paperwork is the whole ugly story: a death in the second year after his death, swallowed by a system that often refuses to name heat even when it helps kill.
NPR, working with Boston University, says federal records show that on average about 1,700 people died from heat-related causes each year in the U.S. between 2018 and 2025. The investigation says the real number is likely about 9,000 heat-related deaths a year, or five times higher than official data suggests, and that even that figure may still understate heat’s deadly impact. Heat rarely arrives alone. It works through the body’s existing injuries, the chronic conditions, the poverty of cooling, and the paperwork that turns a deadly force into “unknown.”
Who Pays for the Heat
Debbie Willson and her son lived in a sun-scorched neighborhood in Tucson. Both were born with DiGeorge syndrome, which caused heart problems. Adam Willson also had cerebral palsy and some developmental delays, and Debbie cared for him full time even after he became an adult. She said he was thriving in his late 20s, loved horror movies, worked at a local movie theater, had written a horror script in his spare time and was looking into film programs to apply to. That life ended in a house that couldn’t stay cool.
Debbie said both she and Adam were highly sensitive to heat because of DiGeorge syndrome. She said too much heat exposure could trigger seizures and strain their already stressed hearts. On really hot days, they would retreat into their house and hope the swamp cooler could keep them comfortable. In June 2024, the swamp cooler broke down. Debbie said money was tight and she couldn’t afford to fix it. The house heated up and stayed hot. She said Adam started having trouble with his heart, and she immediately booked an appointment with his doctor. The morning of that appointment, she found him dead in his room. He was 27.
What the Records Don’t Catch
Quinn Adams, an epidemiologist at Boston University and the lead researcher on the NPR-BU investigation, said there are a number of reasons heat deaths do not show up in state or national death counts. He said heat often worsens preexisting conditions and leaves no obvious mark. “We know that during extreme heat events, a lot of people who die, die because they have preexisting conditions,” Adams said. “Heat is working to make these other conditions worse and make people die faster than they otherwise would have.”
Brian Drummond, an emergency medicine physician in Tucson, said it can be challenging and time-consuming to figure out whether heat contributed to a death. He said when there is no single obvious culprit, doctors may mark the cause as unknown, and in other cases they may record only the most obvious cause, such as a heart attack. He said medical experts know that exposure to heat can stress the heart so badly that it can trigger a fatal event, but doctors, medical examiners and coroners need conclusive evidence to make that link. “If I never ask a patient, ‘Were you exposed to extreme heat?’ or ‘Do you have the ability to cool the place you live?,’ I would never diagnose them with heat-related illness, unless their temperature came in at 105,” Drummond said. He also said, “People are interested in this, but it’s hard,” and added, “It takes time and money and commitment.”
The machinery of death certification matters here. Pima County, Arizona, where Adam lived, has in recent years prioritized asking whether heat played a role in deaths. The county has trained death investigators in the medical examiner’s office to look for faint clues of heat’s influence, including whether a call to an air conditioner technician went unanswered, whether the deceased was taking a medication that suppressed their ability to sense heat, or whether they had a condition such as diabetes or heart disease that made them vulnerable to dehydration or heart attack if their body became overtaxed. Those strategies have improved Pima County’s ability to catch heat-related deaths, and it is one place where official records largely matched the NPR-BU analysis.
The System’s Narrow Lens
Still, many deaths never go to the medical examiner’s office. In Arizona, deaths are investigated automatically if they are suspicious or violent, if they involve diseases of concern to public health, or if the person who died didn’t have a doctor. Adam’s death did not fall into those categories. Debbie said she could have called the Pima County medical examiner to request an autopsy, but she didn’t see the point because Adam was dead either way. Instead, she called the primary care doctor who had seen Adam for years, and he certified the death.
That process is standard practice in many parts of the country, especially when someone has a known medical condition and is under a physician’s care. Changing those practices to more thoroughly investigate the role of heat is far from straightforward. Adams said that without changes for medical professionals, coroners, medical examiners and others who collect death information, the true toll of heat will go drastically undercounted. “That has consequences,” the article says, because when the scale of the problem is unknown, it can’t be addressed appropriately.
Tucson’s heat keeps writing the indictment. June 2024 was hot there, with nearly every day topping 100 degrees and 14 days at 105 or higher. Tucson used to expect less than one day over 110 degrees each year between the 1950s and 1970s, but by this decade that average had risen to nine days a year and had reached as high as 18 in a single year. The city’s annual number of extremely hot days, defined as days whose highs are hotter than 95% of 1991-2020 temperatures, has grown by nearly an entire month since 1970. In 2024, Tucson had a record-breaking 112 days over 100 degrees.
Debbie Willson said she wonders whether her son would still be alive if services had been available to help people like her cope with the heat. She said Adam’s loss is still painfully fresh. “He had his whole life ahead of him,” Debbie said. “He had so much planned for himself.”