Phoenix’s Medical Examiner Seeks Better Count of People Killed by Heat

In Pima County, Arizona, Greg Hess handles death daily, serving as the medical examiner there. He reviews roughly 3,000 deaths annually, including peaceful, quiet ends, overdoses, terrible deaths, and sad ones. During the months from April through October, his morgue drawers swell with people who died before their time due to the oppressive heat.

Pima County is hot, yet it ranks below other places in size, humidity, and population. What sets it apart is the work of Hess and his team, who have built some of the most advanced methods for tracking deaths linked to extreme heat. Their approach is leading the nation when it comes to counting these losses, which could reshape how the country measures the human cost of a warming world. Right now, the true scale of lives lost to climate-worsened disasters is dramatically understated.

The Count Nobody Keeps

Across the nation, a small number of health experts have determined that thousands of Americans lose their lives annually due to climate-driven catastrophes, such as hurricanes that grow stronger and deadlier or heat waves that shatter all previous records. The scale of the issue remains untracked by any official entity — not by government agencies, researchers, or state officials.

Kristie Ebi, a public health and climate epidemiologist at the University of Washington, says those omissions carry real weight beyond the grief of the loved ones of the dead. An inaccurate count of who has died from weather disasters makes it difficult — sometimes impossible — to gauge the true cost to families and communities. That lack of precision also undermines efforts to prepare for and stop these losses from happening again, including figuring out where to place cooling centers during a heat wave, according to Ebi.

“If you don’t know how many people suffer and die in disasters, then you can’t set priorities appropriately,” she says.

A small group is attempting to count better — a vital objective as climate change drives heat toward nearly unlivable temperatures, makes hurricanes deadlier and smothers communities with wildfire smoke. The ranks are varied, ranging from those on the front lines of death, like Hess, to epidemiologists and public health experts. Their aim is to supply insights derived from their data so that policymakers, city leaders and advocates hold the information necessary to save lives.

The Man Behind the Numbers

The desert has proven a congenial home for Hess, whose ruddy cheeks belie his upbringing in Wisconsin. He commutes by bicycle, arriving at work through the hottest months of the Arizona summer without complaint. His prowess on the pickleball court is an open secret: a small silvery cup sits upon his office shelf, with a pickleball jammed inside and a stamped label reading “CHAMPION”, serving as evidence of his standing as the office’s reigning champion.

While he was still studying medicine, he did a rotation in forensic pathology, a post that most other students tried to steer clear of. Why bother with a doctor’s work when the person is already gone, they wondered? He found the very reason that drew him to it: there was something mysterious about those people laid out on the autopsy table, whole lives compressed into the bodies left behind.

His new department head’s first question to Hess concerned his taste in beer, which told him at once that this was the right place for him. He found himself among people whose work was deeply serious yet playful, thoughtful and creative all at once.

While Hess served as an Air Force doctor in California and did a residency in Wisconsin, his time as lead medical examiner in Pima County, Ariz., began in 2011. It was there that he encountered a crisis that would shape his work for years to come.

The Border Crisis That Changed Him

In southern Arizona, Pima County borders Mexico. Its population stands at roughly a million, with most residents settled in Tucson. The remaining land is largely rural, desert broken up by roads dulled white by the relentless sun. When Hess first came to the area, the county drew many people trying to enter the U.S. from Mexico on foot across the border. Yet the desert proved deadly. Every few weeks during summer after summer, Hess received calls summoning his death investigators to a scene where two, or six, or eight people had died from heat and exposure. The yearly tallies climbed well into the hundreds.

As the number of deaths kept mounting without pause, Hess’ group responded by devising fresh approaches to handling each case. They grew skilled at probing fully into every loss, naming those who had died, and locating the family members they left behind, so that those relatives might find some measure of peace. Through this work, Hess came to hold the information his team generated in high regard, seeing what it could accomplish.

Opioids, Then Heat

Not long after, the opioid crisis struck Pima County, filling the autopsy tables at the office with an overwhelming number of cases. Once more, Hess and his team drew upon their earlier experience, gathering comprehensive, detailed information that described and humanized each death. As usual, Hess compiled all the data into tidy annual reports. Yet he believed those reports were largely ignored, sitting on someone’s desktop unread. The reports contained valuable insight, but their usefulness was constrained by the fact that they were “not very timely,” he said.

Around this period, as the opioid epidemic reached its peak, other officials — including those from county public health, the mayor’s office, the police force, and the federal government — came to see that death data could be used to prevent further deaths by spotting patterns quickly and working out how to step in. This would take a quicker sharing of data. So in 2022, Hess was given permission to bring on an epidemiologist, Tasha Tully, to work through the large amount of information the team gathered. Tully built a near-real-time dashboard that followed opioid deaths and sent useful findings straight to city and state offices.

Soon enough, Tully and Hess saw that these kinds of endeavors could also shed light on a different, more subtle epidemic: the rising number of heat-related fatalities that swell their morgue each summer.

Why the Count Matters

The consequences are real and tangible. An inaccurate count leaves cities and counties unable to direct resources where they are needed. It prevents them from placing cooling centers in the neighborhoods that need them most. It also stops them from determining whether efforts — from public awareness campaigns to infrastructure improvements — are working. And it removes any evidence that could be used to support funding requests or policy changes.

When death certificates fail to name a cause, the family is left with an incomplete count of what happened to their loved one. That absence of detail can leave grief feeling unfinished. Knowing the full extent of the problem would not bring anyone back, but it would give survivors a clearer sense of what happened to their loved ones.

What Comes Next

The team led by Hess is expanding the opioid dashboard into a parallel system focused on heat deaths. The idea is to give local officials tools so they can act fast — opening cooling centers, sending out outreach teams, changing public health messaging — before the next round of hot weather arrives.

In Pima County, local leaders have shown how data can be used to deal with climate effects. The county’s records prove that even a small area can produce information that matters nationwide. Hess and his team are not simply tallying deaths; they are measuring what a warmer planet costs.

Key Dates in Pima County’s Heat Tracking Efforts

The Case for Better Data

There are several reasons why accurate heat death tracking matters:

1. It helps families find closure by providing clear, consistent information about how their loved ones died.
2. It allows cities and counties to target resources — cooling centers, public health campaigns — to the neighborhoods that need them most.
3. It provides a baseline for measuring the effectiveness of interventions.
4. It gives policymakers evidence to support funding and policy changes.
5. It improves the overall understanding of how climate change affects public health.

For years, the nation has failed to fully account for how climate change affects people. Pima County is working to correct that problem. Other regions would do well to watch what happens there.

Arizona · climate change · heat deaths · medical examiner · public health