Study finds US prisons and jails face increasing number of days with dangerous temperatures

Marci Simmons remembers her days in Texas State Prison as a cruel game of psychological summer planning. “In April, you start preparing for the heat,” she said. “Towards the end of May, when it starts to get hot, you start saying, ‘OK, it’s only four months of this really bad heat.’ And then you start counting down in your mind. It’s a mental game of survival.”

Simmons had been incarcerated in Texas State Prison for more than a decade, serving her sentence in the Dr. Lane Murray Unit, a state prison for women in Gatesville—one of many such facilities around the country that lack air conditioning in their living quarters. To stay cool on hot days, she and other women lay on the floor of their cells in pools of water drawn from sinks.

She said she wasn’t always able to keep track of the room’s temperature because maintenance workers kept a piece of duct tape over the dorm’s thermostat to hide the temperature readings. But on a hot day in the summer of 2020, Simmons removed the duct tape using the sticky sides of two maxi pads she’d attached to the end of a broom. The temperature was 136 degrees. “I thought, well, that’s why they didn’t want us to know,” she said.

The study, published in March in the journal Nature Sustainability puts their experiences in a national context. Assessing heat exposure in more than 4,000 U.S. prisons, jails, and immigration detention centers since the 1980s, researchers found that the number of hot days per year has increased in more than 1,000 facilities — mostly in the South. They found that Texas, Florida, Arizona, and Louisiana had the highest exposure to potentially dangerous heat days — yet none of them provide widespread air conditioning in state prisons.

Overall, state prisons in Texas and Florida were the most exposed to dangerous heat, researchers found, accounting for 52 percent of the total exposure to dangerous heat despite housing 12 percent of America’s prison population. The researchers say the study sheds light on the urgent need to improve infrastructure and policies to protect prisoners from the extreme heat hazards they can’t escape.

The study was inspired by the stories of incarcerated people that are published in the media every summer, said Robbie Parks, an environmental health scientist at Columbia University who co-authored the study. “People are dying without any cooling. That inspired us to try to understand, ‘What is the actual heat exposure of incarcerated people? And what is the disparity compared to the rest of the country?’” he said. “Of course, the climate is changing. But it turns out that prisons are in places that are actually set up for higher temperatures.”

To conduct the study, researchers mapped the location and population of every prison, jail, and immigration detention center in the U.S. using data from the U.S. Department of Homeland Security. They assessed heat exposure at those locations using weather data recorded between 1982 and 2020 by researchers at Oregon State University. They then compared temperatures at those locations with those elsewhere.

The researchers defined potentially dangerous heat days using a standard used by the U.S. National Institute for Occupational Safety and Health (NIOSH) called “wet-bulb temperature,” which takes into account a number of factors, such as humidity and air movement, to measure heat stress in workers. NIOSH defines the maximum wet-bulb temperature as 28 degrees Celsius, or 82.4 degrees Fahrenheit, for workers performing sedentary tasks with moderate levels of physical activity. (When temperatures rise above that threshold, worker accidents increase, according to a 2016 NIOSH report.)

Researchers found that 118 prisons, mostly in Southern California, Arizona, Texas and Florida, had temperatures above NIOSH’s dangerous temperature threshold an average of 75 or more days per year. Air conditioning is not widely available at these facilities, and some rely on evaporative cooling systems, which are not as effective, according to the researchers.

They also found that prisons are disproportionately exposed to dangerously hot days compared with other areas of the U.S. Arizona, California and Nevada ranked in the top three states with the largest temperature differences between areas with and without prisons. While climate change is certainly a driving force, the location of those facilities also plays a role, the researchers said. Prisons and jails are often built where land is cheap and communities are spread out. Historically, they tended to be located in isolated deserts or swampy areas.

Ladd Keith, an urban planner at Arizona State University who studies the health risks of extreme heat, said the study is significant because it examines the entire U.S. prison system, rather than a single state or a single type of prison. “I think it presents a really holistic picture of the risks of heat for incarcerated people,” he said.

Other studies have assessed environmental exposures of prison populations in specific states. A 2023 study from the University of Colorado found that most people incarcerated in the state are exposed to extreme heat, among other environmental hazards. A 2022 study led by a Brown University researcher found that Texas’ prison mortality rate is 30 times higher than the national average, likely due to heat-related deaths and lack of air conditioning.

The researchers noted that the risk of exposure to extreme heat may be particularly serious for incarcerated people with mental illness, since many psychiatric medications can impair the body’s ability to regulate heat. About 43 percent of people in state prisons report a history of mental health problems, according to the U.S. Department of Justice.

The next step in the research, Parks said, is to map indoor cooling systems in prisons across the country, along with heat-related deaths and illnesses that have been reported in those facilities. Risk factors for heat-related death or illness should also be assessed. “We want to know what we can change in the current conditions in prisons and jails to actually mitigate potential risks associated with indoor heat,” he said.

Recent legal scholarship argues that as climate change worsens conditions in U.S. prisons, constitutional protections against cruel and unusual punishment could be undermined. But incarcerated people may have few effective means of seeking justice for such violations, the researchers write, because federal courts, particularly in the South, have historically been unfriendly to incarcerated people bringing claims of cruel conditions.

Simmons said she filed formal complaints with the prison system every summer for 10 years, asking for relief from the extreme heat. “They just said there was nothing they could do,” she said. “It was very ineffective.”

Now she receives letters from people in the hospital telling her about the different ways they are trying to survive — like stopping psychiatric medications that come with a warning about high temperatures.

Simmons said she was lucky to be trapped without any underlying health conditions that could have put her at risk for heat illness. Still, she said, “I thought I was just going to die because it was so bad.”