Extreme and prolonged heat waves have engulfed much of the United States this summer, with last month ranking as the warmest July on record for the Lower 48, according to the National Oceanic and Atmospheric Administration.

As climate change drives up temperatures and makes heat waves more extreme, conditions are becoming increasingly dangerous for the nearly 2 million people in carceral facilities across the country, said David Ciplet, associate professor in the Department of Environmental Studies. At least 44 states lack universal air conditioning in their prisons. 

“There's just a huge amount of need for better living conditions in prisons, and the harms are just so extreme,” said Ciplet, who leads the Climate and Incarceration Research Collaborative, an interdisciplinary team that includes scholars from universities around the country, some of whom are formerly incarcerated.

 
David Ciplet

David Ciplet

The project aims to understand incarcerated people’s experiences inside prisons in relation to climate risks, including extreme temperatures and wildfire smoke, and identify policies that could improve conditions inside these facilities and reduce the number of harmful prisons nationally. 

It is unclear how many of the more than 3,500 deaths each year in U.S. state and private prisons are a result of extreme weather, because most facilities don’t properly track or report them, according to The Appeal, a non-profit news organization focusing on criminal justice. But a previous study has found that about 13% of deaths in Texas prisons during warmer months could be a result of heat.  

Climate change disproportionately affects marginalized communities, who often have the least resources to cope with the impacts, Ciplet said. 

“Incarcerated people have the least agency and ability to control their environment, but their experiences tend to be invisible to the general public,” he added.

Heat behind bars

The past July was the second-hottest on record in Colorado, with many parts of the state, including the Denver metro area and northwest Colorado, experiencing their hottest July ever.

While there is no national standard for temperatures inside prisons, the state of Colorado requires indoor temperatures in correctional facilities to remain below 86°F during the warmest months. 

That threshold is considerably higher than recommendations from health authorities, including the World Health Organization, which suggests limiting indoor temperatures to below 75°F. 

Because prison temperature data are often not publicly available, it remains unclear if facilities enforce the standard, Ciplet said.  

“What we’re seeing in Colorado and elsewhere is that we are having more frequent extreme heat that lingers. It’s one thing if you have one really hot day, but if you are exposed to seven or 10 days that are extremely, extremely hot, that’s going to have compounding impacts on health and your body’s ability to process those temperatures,” Ciplet said.

The team is working with 15 participants who were formerly incarcerated at four state prisons throughout Colorado to understand the conditions inside the facilities. Their accounts paint a grim picture behind bars. 

While Colorado state prisons have swamp coolers that can keep common areas cooler, the cold air does not always reach the cells, according to the participants. Some south-facing cells at the Fremont Correctional Facility in central Colorado can reportedly reach temperatures above 90°F in the summer. 

Trevor Jones had spent two and a half years at Fremont. While he stayed in a north-facing cell, he said the 60-year-old facility wasn’t built to deal with extreme heat or cold.

In addition to the lack of air conditioning, incarcerated people also have very limited options to stay cool. Jones said that people can order a fan if they can afford it, but the item isn’t always in stock, and it usually takes a month for the order to arrive. 

“But when it’s really hot, all a fan can do is push the hot air around,” he added. 

Participants also mentioned that their showers would only run at very hot temperatures, even during the peak of summer. In women’s prisons, they said, people are required to sleep fully clothed, regardless of how hot it is. 

During extreme heat days, incarcerated people may still have to stay in the recreation yard, which often has no shade, or work in areas such as kitchens, where temperatures can be 20 or 30°F hotter than elsewhere in the facility.

Medication can add another layer of danger, Ciplet said. Many incarcerated people take medicine to treat conditions such as depression and anxiety, and those drugs can prevent the body from coping with high temperatures effectively.

Those risks can become even more severe in solitary confinement, where people have even less access to showers, water and fewer opportunities to leave their cells.

“There are all these ways that the rules that they’re subjected to on a daily basis can take something like 85 degrees, which is still quite hot, and make it much more unsafe,” Ciplet said.

Seeking solutions

The team is working with participants to identify the biggest challenges they faced and develop policy suggestions to push for changes.

For example, they suggest that reducing prison populations could avoid overcrowding, which can make hot environments even hotter. They also hope to advocate for better infrastructure, including regular maintenance of ventilation systems and greater access to cooling devices.

The research, led by formerly incarcerated people, also aims to provide participants with skills that could help them pursue future employment opportunities, Ciplet said. “Some of them are really interested in becoming researchers or advocates to help others,” he added. 

The collaborative is also working with advocates in Texas, where policymakers considered a bill last year that would have required prisons to have air conditioning by the end of 2032. The bill died in the state Senate. Colorado has yet to introduce a similar bill.

“A society is only as healthy as its most marginalized people,” Ciplet said. “If we can design climate policy with those people at the core of it, we have the best chance of moving toward a better society.”

Through the project, the team hopes to draw more attention to the worsening conditions incarcerated people face, an issue that is usually out of public sight.

“Reducing the quality of life for someone who's incarcerated doesn't add to the interest of justice,” Jones said. “What are we as a society if we think the humane way to treat people who need societal help is to throw them into a hot or cold cage?”

Source: https://www.colorado.edu/today/2026/09/02/people-behind-bars-extreme-heat-can-be-deadly-and-inescapable