Emerging patterns of heat and wildfire smoke at California correctional facilities

Abstract

Climate change has intensified and increased the frequency of extreme heat and wildfire smoke events, posing growing risks to health in carceral settings where infrastructure limitations and regulatory gaps heighten vulnerability. This study characterized temporal trends and geographic patterns in extreme heat and wildfire smoke exposure across 410 California correctional facilities from 2000–2023. We used ERA5-Land reanalysis data to calculate daily maximum temperature and identified days exceeding the 28 °C threshold corresponding to California’s indoor heat illness prevention standard. Wildfire smoke PM2.5 exposure was estimated using a validated statistical model generating daily ground-level predictions at 10 km resolution. Temporal trends were modeled using facility-level linear regression. Mean wildfire smoke PM2.5 concentrations rose from 0.4 µg m−3 (2006–2010) to 1.4 µg m−3 (2019–2023), a 3.5-fold increase, with Northern California experiencing the highest burden and steepest increases. Annual days above 28 °C increased from 27.3% to 29.8% statewide, with the Central Valley and desert regions showing the highest current burden. On average, facilities experienced 6.8 dual heat and smoke burden days per year during 2019–2023, with Central Valley and Sierra foothill facilities most affected. These findings underscore the need for region-specific mitigation strategies and updated regulatory protections for people living and working in California correctional facilities.