This article draws on the stories of formerly incarcerated people to examine the ways in which the physical and social infrastructures of carceral facilities increase incarcerated people's vulnerability to environmental hazards exacerbated by climate change. We present qualitative data from interviews and focus groups with people who have been incarcerated in prisons and/or jails in Colorado regarding their experiences with incarceration infrastructure, amplifying the voices of formerly incarcerated people to identify vulnerabilities which have been deliberately hidden by carceral social and institutional processes, and adding them to the academic dialogue around incarceration and climate change. By providing testimony on the ways in which incarceration infrastructure—how they are designed, built, and maintained—amplify environmental harm, we identify how incarceration infrastructures create environmental vulnerability along axes of temperature, air quality, and water supply even before incarcerated people are exposed to climate hazards. Then, we illustrate ways incarcerated people encounter limits to their agency to mitigate this vulnerability, suggesting the need for structural change. Finally, we provide evidence that climate-related extreme temperatures, wildfires, and flood events experienced by our participants exploited the axes of vulnerability laid out above, affecting the majority (65%) of our 35 study participants. Overall, we argue current carceral infrastructure creates material realities that regularly cross the threshold of cruel and unusual punishment, and our argument supports decarceration as a necessary public policy intervention for robust, just, and humane climate resilience.