extreme heat

Op-ed: We are undercounting heat-related deaths in the US

Knowing how many people die or get sick from heat-related causes is essential for the policy arguments to equitably adapt to and mitigate climate change.

In summer 2022, in San Antonio, Texas, 51 migrants died in an overheated truck, after being smuggled across the border from Mexico.


The day they died, temperatures peaked well past 100 degrees Fahrenheit (38 degrees Celsius), and the truck had no water and a busted cooling system. Eleven people survived thanks to a nearby worker who heard muffled cries for help. Though their deaths are in part due to the negligence of their driver, extreme heat also played a big role. However, their deaths — like thousands of others in the U.S — were likely not recorded as heat related. This common oversight is a problem that obscures the deadly effects of rising temperatures.

Heat is estimated as the number one weather-related killer in the U.S. Exposure to elevated heat can directly result in heat cramps, heat exhaustion, heatstroke and hyperthermia. Elevated heat can exacerbate chronic conditions such as asthma, heart and other cardiovascular diseases, autoimmune conditions, arthritis, and can deteriorate mental health. Knowing how many people die or get sick from heat-related causes is essential for the policy arguments to mitigate climate change, as well for environmental justice — we need to know how many people are dying and who they are.

One major step to doing this is making sure that we are thoroughly and accurately accounting for all the people who are losing their lives to heat. But exactly how many people are dying due to heat? The numbers we have now are almost certainly underestimating the true death count attributable to elevated heat. The Environmental Protection Agency (EPA) estimates 600 annual deaths attributable to elevated heat, while statistical approaches estimate more than 1,300 annual deaths.

The role of medical examiners 

There are two types of heat-related deaths: heat stress deaths, caused directly by heat and recorded on a death certificate; and heat-exacerbated deaths, when heat worsens existing chronic conditions. Heat can be listed on death certificates as a contributing or underlying cause of death. However, many deaths associated with elevated heat are not identified as such by medical examiners and might not be properly coded on the death certificate, as the EPA notes. If the cause of death is classified as the result of a cardiovascular or a respiratory disease, the medical examiner may omit the role of heat in the death if they are uncertain whether it was a contributing factor. Moreover, when making such a determination, there is a lack of standardization in how medical examiners quantify heat. As per the Medical Examiners’ and Coroners’ Handbook on Death Registration and Fetal Death Reporting, the cause of death is the medical examiner’s best medical opinion and, in some cases, where it is not possible to make a precise determination of the interacting causes of death, a subjective call has to be made.

It doesn’t help that each state possesses an independent system. As of 2019, 16 states had a centralized medical examiner system, 14 had a county-based system with a mixture of coroner and medical examiner office, six had a county- or district-based medical examiner system, and 14 had a county-, district- or parish-based coroner system. Medical examiners and coroners are substantially different. While medical examiners are appointed and have board-certification in a medical specialty, coroners are elected lay people who often do not necessarily have professional training. The lack of standardization in state systems as well as in how medical examiners determine whether heat is an underlying factor of deaths contributes to the uncertainty of how many people die of elevated heat.

No standards to tally heat-related deaths

extreme heat

When making a determination of cause of death, there is a lack of standardization in how medical examiners quantify heat.

Credit: artistmac/flickr

Though states and researchers also use statistical models to estimate the numbers of heat-related deaths, the methods are not standardized. Approaches can range from using two models that reflect different measures of hot weather – which is New York City’s chosen method – to time regression studies. Moreover, even if researchers do use the same methods, there are also different approaches to estimating minimum mortality temperatures, which can lead to different estimates of excess deaths. Since these numbers are often the ones circulated, the extent to which these methods differ opens the door for discrepancies. With the lack of a standardized approach, we propose developing a unified U.S.-wide method of excess heat-attributable deaths immediately.

Evidence for climate change action  

There are many policy makers who may not see the point of such measures. For a large portion of history many politicians denied that rising temperatures were an issue. And now, polls show that though Republicans are open to some policy approaches, climate change is still considered a low priority. So, why do these details matter? We need to know how many people are suffering in order to effectively drive policies for climate and health action. Each heat-related death was a life and represents a story that ended too early. When the public hears about stories such as the migrants’ deaths in San Antonio, they are rightly shocked. If they knew the full extent of how heat kills in the U.S., they would be able to put further pressure on lawmakers to spur climate change action. Our health depends on the climate’s health.

Even if researchers do use the same methods, there are also different approaches to estimating minimum mortality temperatures, which can lead to different estimates of excess deaths.

Identifying and mitigating heat-related deaths is also relevant to the historically underserved communities that are the most exposed and vulnerable to elevated heat. In the rural parts of America, Latinos make up nearly 60% of farm laborers, an occupation infamous for having limited protection against the heat. Meanwhile in cities, racist policies and urban planning decisions from decades ago have created redlined neighborhoods that are much hotter and deadlier than other areas. Black and Brown communities are enduring the brunt of the heat’s wrath. By more accurately identifying which groups of people are disproportionately suffering the most, we can push lawmakers to take more action to avoid more heat-related tragedies.

What happened in San Antonio was a tragedy, but it was not an accident. If we don’t start taking action now, there are only more dire ‘accidents’ awaiting us. It is scary not knowing what you are up against — so improving our knowledge of heat-related deaths is the first, and one the most important, steps.

three windmills on top of a hill with blue sky and clouds behind.

Trump administration redirects clean energy funds in defiance of Congress

The U.S. Department of Energy (DOE) is cutting funding for wind, solar, and electric vehicles despite a signed federal budget that preserved those levels, prompting accusations of unlawful spending violations.

Zack Colman reports for POLITICO.

Keep reading...Show less
Sign saying Break Free from Fossil Fuels on a street.

Burning fossil fuels linked to 1,500 deaths in Europe’s latest heat wave

A new analysis directly attributes about 1,500 deaths in 12 European cities last week to the intensifying effects of climate change caused by fossil fuel emissions.

Seth Borenstein reports for The Associated Press.

Keep reading...Show less
Blue European Union flags flying in front of a building.

Far-right group takes lead in EU climate talks, raising doubts over 2040 emissions goal

The far-right Patriots for Europe bloc will lead the European Parliament’s negotiations on the EU’s proposed 2040 climate target, placing a group hostile to existing climate policies at the center of the talks.

Kate Abnett reports for Reuters.

Keep reading...Show less
Wind turbine, solar panels and nuclear cooling towers with a blue sky in background.
Credit: jaroslavav/BigStock Photo ID: 83377346

Solar is no longer alternative energy—it's the new default

Around the globe, solar power is scaling up at a breakneck pace, reshaping energy systems, economies, and even geopolitics.

Bill McKibben reports for The New Yorker.

Keep reading...Show less
A power plant with a wind turbine in the foreground.

Shanxi province faces difficult path away from coal as China pushes clean energy

China’s top coal-producing region, Shanxi, is struggling to pivot from its fossil-fueled past to a cleaner economic future, as the country races to meet ambitious carbon targets by 2060.

Amy Hawkins reports for The Guardian.

Keep reading...Show less
A flooded park alongside a river with submerged trees.

Texas growth and lax rules put more homes in harm’s way from flood disasters

As deadly floods strike Central Texas, experts say outdated maps, weak regulations, and rapid development are funneling millions of Texans into flood-prone areas with few safeguards.

Joshua Fechter and Paul Cobler report for The Texas Tribune.

Keep reading...Show less
Rural hills under dark storm clouds during daytime.

Trump administration moves to shut down critical storm research lab in Oklahoma

The Trump administration has proposed closing more than two dozen federally funded meteorological labs, including Oklahoma’s National Severe Storms Laboratory, sparking bipartisan concern over public safety and economic consequences.

Emily Kennard reports for NOTUS.

Keep reading...Show less
From our Newsroom
Multiple Houston-area oil and gas facilities that have violated pollution laws are seeking permit renewals

Multiple Houston-area oil and gas facilities that have violated pollution laws are seeking permit renewals

One facility has emitted cancer-causing chemicals into waterways at levels up to 520% higher than legal limits.

Regulators are underestimating health impacts from air pollution: Study

Regulators are underestimating health impacts from air pollution: Study

"The reality is, we are not exposed to one chemical at a time.”

Pennsylvania governor Josh Shapiro speaks with the state flag and American flag behind him.

Two years into his term, has Gov. Shapiro kept his promises to regulate Pennsylvania’s fracking industry?

A new report assesses the administration’s progress and makes new recommendations

silhouette of people holding hands by a lake at sunset

An open letter from EPA staff to the American public

“We cannot stand by and allow this to happen. We need to hold this administration accountable.”

wildfire retardants being sprayed by plane

New evidence links heavy metal pollution with wildfire retardants

“The chemical black box” that blankets wildfire-impacted areas is increasingly under scrutiny.

Stay informed: sign up for The Daily Climate newsletter
Top news on climate impacts, solutions, politics, drivers. Delivered to your inbox week days.