How many people died in the Phoenix heat? Finding the answer takes time for investigators

The first death of the heat season came on a Tuesday in April, when the mercury tipped 99 degrees.

The temperature was a record, the hottest April 11 in nearly 130 years, and it claimed the life of a 42-year-old woman. The primary cause of death: acute methamphetamine intoxication. A contributing factor: heat.

In the days and months that followed, more records would shatter and more people would succumb. It was the hottest summer on record, in the hottest big city in the U.S.

Across the heat season, the number of people who died from heat in Maricopa County was 579 — and counting.

This grim tally is compiled by the county Office of the Medical Examiner, led by Dr. Jeff Johnston.

Though temperatures have since eased, for Johnston and his staff, the heat season still isn’t over. There are still deaths to investigate, records to pore over, and reports to write, detailing whether heat played a role in someone’s death.

The OME braces each year for a summer surge, the busier of its two peak seasons. (The other comes in winter, when snowbirds flock to metro Phoenix from colder climes and, sometimes, die outside of the care of their usual physicians.)

“This last summer was really challenging,” Johnston said, in a recent interview with The Republic. “The summer before, it was really challenging as well.”

Typically, July and August bring in about 25% more cases than the average month, Johnston said, an increase his office is well-equipped to handle.

In the summer of 2023, the increase was 63%.

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What determines if someone has died from heat?

Though not yet final, the number of heat-associated deaths in Maricopa County in 2023 has already eclipsed the previous record of 425, set in 2022. That figure was in turn higher than the 339 who died from heat in 2021.

Summers in Phoenix are getting longer and hotter, fuelled by global climate change and the “heat island” effect of sprawling concrete and asphalt.

But there are other factors at play. An uptick in the city’s unsheltered population has exposed more people to the searing heat without respite. Certain drugs, particularly methamphetamines, sap humans of their ability to withstand heat. Cost of living pressures might mean an elderly person doesn’t put the AC on when they really need it.

These problems are captured in death by Johnston and his team.

It’s a misconception that once the autopsy is done, all questions are answered, Johnston said. Most of the time, that’s just the beginning.

This is particularly so for heat deaths, which don’t leave telltale signs on the body. Blunt force trauma may be obvious even to a layperson, a stroke rapidly apparent to a forensic pathologist’s eye. But the dysfunction wrought by intolerable temperatures leaves no specific signature.

“It’s really more looking for other things that would make heat not relevant any more,” Johnston said.

These investigations, each led by a forensic pathologist, go beyond the autopsy table. Just like doctors that treat the living, the staff will obtain a medical history. They might test blood for drugs or poisons, or scrutinize tissue under a microscope. Medicolegal death investigators, who examine the decedent through a medical and legal lens, study and photograph the scene where someone died, noting details such as whether the AC was functioning, conduct interviews with family and other witnesses, and make record requests.

“It really has to be looking at the whole picture,” Johnston said.

Heat-associated deaths, as they are termed by Maricopa County, don’t all look the same. The county draws a distinction between deaths caused by heat, meaning environmental heat exposure is the primary reason a person died, and deaths related to heat, where it is a contributing factor.

Someone who goes out hiking and gets dehydrated and dies, and on examination is revealed to be otherwise healthy, with no drugs in their system, is likely to be classified as a heat-caused death.

Another person might die on the same day, but with multiple risk factors. Perhaps they have a substance use disorder and were using methamphetamines prior to death, or an underlying natural disease, or both. In those cases, the pathologist must determine what loomed most large.

“So in some cases, it may be an acute methamphetamine intoxication is kind of the primary cause, but heat is listed as a contributor,” Johnston said. “Or vice versa, it could be that the heat is really the primary thing that we think is operating, and those other conditions are contributory.”

The county includes both heat-caused and heat-related deaths in its final tally, but most jurisdictions around the country only include the former. Of the 579 deaths recorded in the final weekly report for 2023, 330 were heat-caused and 249 heat-related.

Wherever the distinction lands, the heat is crucial.

“If it wasn’t for the heat,” Johnston said, “we don’t expect that that person would have died.

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Managing the surge as temperatures rise

In late July, the OME refrigerators hovered on the brink of capacity.

The office maintains a flow of bodies in and bodies out, giving staff members time for their examinations and families time to decide on a funeral home before the remains are released, freeing up space.

But Phoenix was in the grip of a 31-day streak of temperatures above 110 degrees, and bodies had come in thick and fast, disrupting the regular cadence.

The office had a contingency plan that would be triggered once there was a risk of filling up in the seven days that followed. They had come close to activating it in 2022, Johnston said, but didn’t quite cross the threshold.

“But then this past summer,” he said, “we did.”

Ten refrigerated storage units were trucked into a downtown Phoenix parking garage close to the office. Their foreboding presence received significant local and national media coverage. The heatwave ground on, finally breaking — if you can call a high of 108 respite — on July 31.

But the units stayed empty.

“We ended up not having to use them, fortunately,” Johnston said. Still, the summer was taxing. “It's still a stress on us for sure, and risky to the operation too, just when you have those levels of surges.”

But he said foundations laid in recent years, including accreditation, filling high-demand forensic pathologist positions, and a change that sped up next-of-kin notifications, had allowed his officethem to weather the storm.

“Things would look a lot different if we hadn’t had those,” Johnston said.

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Heat deaths challenge investigators

Ideally, the office would be able to bring in a summer surge staff. But finding one is difficult for the highly specialized jobs within the OME.

Forensic pathologists are in short supply across the country. Other roles, such as medicolegal death investigators and forensic autopsy technicians, lack external training programs. These staff learn on the job, and it can take two or three months before they are ready to work autonomously.

“We're one of the busiest (medical examiner) offices in the country and are, you know, three or four times bigger than our next biggest county, Pima County,” Johnston said. “And so there's really nobody to pull from.”

Striking a balance is especially challenging as a public agency that must be able to justify its resources. A staff that could easily handle a 63% surge would be too large for the quieter months.

“It’s this constant chicken and egg sort of thing,” Johnston said.

And it’s tough work, getting up close with death.

Heat deaths can be particularly confronting, as they tend to occur among society’s most vulnerable: people who are unsheltered, people who have substance abuse disorders, and older people.

“Certainly we come into this work, in this form of public service, knowing that we're going to see a lot of tragedies,” Johnston said.

“So we do have to be careful about those trauma exposures and, you know, be a little bit wary about putting ourselves in the shoes of those vulnerable people and the tragedies that have befallen them, because it becomes a risk for us to be able to function and do our jobs.”

The medical examiner field has come a long way in this regard, Johnston said, better at talking about trauma exposure and how to stay resilient in its glare.

His office has several measures for supporting staff, including quiet rooms where people can decompress from challenging scenes, giant murals for coloring, therapy dogs, and trained peer support groups, where staff can debrief among people who truly understand what they are going through.

“Certainly, sometimes these things all hit us and it's impossible for it for it not to,” Johnston said. “And really our goal is just to support people when they do so they can recover and keep going.”

Understanding the risks of living in a hot city

Johnston isn’t sure when the heat season will end for his office.

The majority of heat-associated death reports will be finished before December, but a handful may linger through the holidays. Some investigations take longer than others, especially those involving records requests, which can take a while to come through and then, occasionally, open a whole new line of inquiry.

Johnston said his office completes well over 90% of reports within three months, which is the industry benchmark. As for the rest, 99% are done in six months and 100% in a year.

“Ultimately, we need to have some conclusions about these,” Johnston said. “Because so many stakeholders need information from us.”

It’s the reason his office exists: to investigate those who die, in order to help those who are alive.

The death data goes to county public health, where it is studied in the hope of identifying potential interventions to stem the flow of people dying from heat.

Johnston said there is room for more research and education on not only understanding the hazards of extreme heat, but also responding appropriately to prevent deaths.

“One of the real challenges we have in the Sonoran Desert is that, you know, in cold environments that are dealing with sort of that hazard, you can look outside and see if it's a blizzard,” he said. “There's a real visual change in how things are.”

“But for us, the summers are always hot, and what's too hot can feel the same as you walk out the door as something that you could probably have tolerated a week ago.”

Typically only a third of heat-associated deaths occur during National Weather Service excessive heat warnings, he said.

More education on risks — such as people learning to check U.V. exposures and other factors alongside the temperature — could lead to better decisions, like skipping a regular hike, or checking on an elderly neighbor who was having AC trouble.

“If everybody's sheltered and everybody has adequate air conditioning and nobody's going outside to work in their yard when it's dangerous outside,” Johnston said, “then it doesn’t matter how hot it is — we’re all still going to be fine.”