Vulnerable groups such as older people, pregnant women, and children are particularly affected. Elevated temperatures during heatwaves exacerbate air pollution, increasing concentrations of pollutants such as ozone (O₃), particulate matter (PM₁₀), and nitrogen dioxide (NO₂), which further drive hospitalisations for cardiovascular and respiratory conditions. Moreover, extreme heat has been associated with negative mental health effects, including increased aggression, irritability, and a higher risk of suicide, particularly among vulnerable groups such as those from lower socio-economic backgrounds, adolescents, older adults, individuals with preexisting health conditions (whether mental or physical), and those living in inadequate housing. Heat-related deaths are expected to rise, and without adaptation measures, this could increase 6-fold by 2050 compared to the 2007-2018 level.
Heat is a priority risk for the NHS in England, as healthcare infrastructure is generally ill-equipped to handle extreme temperatures, with air conditioning not routinely installed and poor ventilation. Approximately 90% of England’s hospital buildings are vulnerable to overheating, with NHS estates experiencing high indoor temperatures even during moderately warm summers; some wards have recorded temperatures exceeding 30ºC when outdoor temperatures are just 22ºC. NHS England standards recommend ward temperatures between 18ºC and 28ºC, and 18ºC to 25ºC for sensitive areas like birthing and recovery rooms. The incidence of overheating at NHS sites in England has nearly doubled from 2,980 incidents in 2016–17 to 5,554 in 2021–22. For example, during the July 2022 heatwave, IT systems at Guy’s and St Thomas’ NHS Foundation Trust failed due to overheating, triggering a critical incident that disrupted clinical services for several weeks. Beyond compromising patient safety, excessive heat poses occupational health risks, discomfort, and reduced productivity for healthcare staff.
Similarly, overheating in hospitals throughout the rest of the UK is a significant concern, yet there are currently no systems in place to report instances of overheating in healthcare facilities in Scotland, Wales, and Northern Ireland. Public Health Wales has recognised that without a reporting system in place, it is not currently possible to quantify the impacts of higher temperatures on the resilience of NHS Wales services.