Skillful heat-related mortality forecasting during recent deadly European summers.

Europe is a heatwave hotspot: numerous temperature records have been broken in recent summers, and roughly 60,000 and 50,000 heat-related deaths occurred in the summers of 2022 and 2023, respectively. With recent summers, like that of 2022, projected to become the new norm, there is a pressing need to further develop heat-health warning systems to help society adapt to a warming climate. Here, we forecast heat-related mortality by applying a statistical epidemiological framework to temperature forecasts extending up to 2 wk in advance. Focusing on two recent and exceptional summers in Europe, namely 2022 and 2023, we evaluate the skill of the daily heat-related mortality forecasts, and assess its association with temperature. For most of Europe, milder temperatures, close to the minimum mortality temperature, are associated with more skillful heat-related mortality forecasts. However, some of the hottest regions in Europe instead showed enhanced forecast skill associated with higher temperatures. This suggests that heat-related mortality forecasts can provide valuable information in European regions associated with high levels of heat-related mortality. Consequently, we advocate for local health authorities to include information from forecasts of heat-related mortality in their heat warning systems.