Open AccessHeatwaves have well described impacts on human health and wellbeing. Heatwaves also have impacts on hospitals. Patients, visitors, equipment, medication and IT systems have all been affected or compromised during episodes of extreme heat. High indoor temperatures are also of concern for the comfort, efficiency, and occupational health of staff. The Heatwave Plan for England describes actions to prepare for and be taken in the event of a heatwave. Advice for a hospital is so far limited and not evidence based. In this paper, we review what is currently known about the impacts of heatwaves on hospitals and identify several important information gaps. Improved responses to hot weather could improve patient care and staff comfort. If seen as part of a wider approach to sustainability, proper planning will also enable hospitals to reduce health care costs, increase efficiency and meet carbon reduction targets.