Heatwaves and extreme weather events are now commonplace. States across the South and Southwest are experiencing record high temperatures (during the day and at night, which is a big deal). Meanwhile, the Northeast has been drenched in more frequent, torrential rainfall and flash flooding. Prisons and jails nationwide aren’t insulated from these events, yet we rarely see how bad the conditions are for the millions of people locked within them.

Hopefully, readers have seen our prior work — or any of several other powerful essays — explaining the ways in which extreme heat, combined with a lack of air-conditioned spaces and cooling measures, is especially harmful to people behind bars. Some have described the experience as being trapped in heat-retaining “convection ovens.” We’ve also highlighted some of the environmentally disastrous ways prisons are sited and operated.

In this briefing, we present new findings from a nationwide, epidemiological study showing a strong relationship between extreme heat and deaths in prisons — especially in the Northeast. We also explain why extreme heat isn’t an isolated danger — it’s wrapped up in other hazards like pests and diseases guaranteed to make prison life miserable, if not fatal.

A group of researchers, led by epidemiologist Julianne Skarha, offer new evidence that the heat we’ve been experiencing is particularly deadly for incarcerated people across the U.S. Using two datasets — annual deaths in state prisons from the Bureau of Justice Statistics, and hourly temperature data from the North American Land Data Assimilation System — the researchers looked at unusually high temperatures occurring in the summer months at the geographic location of prisons.

Using established public health research methods, the study’s authors were able to look at exposure to a “risk” or an event — in this case, hotter-than-average days or multi-day heatwaves, and observe an acute outcome — deaths in state prisons (categorized as suicide, heart disease, or death from any cause). They examined deaths that occurred up to three days after each heat event.

As expected, unusual heat was associated with higher overall mortality. The researchers found for every 10 degree increase above the prison location’s mean summer temperature, nearly 5% of deaths (from all causes) occurring there could be attributed to the heat. Even the days following a hotter-than-average day were associated with deaths, although the risk of heat-related death declined, suggesting that mitigating heat right away is crucial.

Read the full article about climate change and prisons by Leah Wang at Prison Policy Initiative.