Heat-related mortality in Europe during the summer of 2024: capacity of early warnings to anticipate the burden and prevent deaths

The year of 2024 was the warmest on record, both globally and in Europe, and the first to exceed 1.5°C in global mean temperature above the preindustrial level. Successive record-breaking temperatures in recent years emphasized the urgent need to develop and implement a new generation of impact-based early-warning systems (EWS), using epidemiological models to transform weather forecasts into health predictions (see https://forecaster.health/).

Here we combined the newly created daily continental mortality database of the EARLY-ADAPT project (https://www.early-adapt.eu/), the open-access Eurostat weekly mortality database, ensemble weather forecasts from ECMWF, and temperature observations from ERA5-Land to (i) estimate the heat-related mortality burden during the summers of 2022-2024, and (ii) analyse the forecast skill of the novel heat-health EWS.

The record-breaking temperatures of the 2024 were associated with the highest heat-related mortality burden in Greece, Bulgaria, Serbia and Romania. Our analysis showed that the impact-based EWS can predict heat-related mortality burden at least six days in advance, even during exceptionally warm summers. However, when considering extreme temperatures (> 95th percentile), the temporal prediction window is shorter, with a lead time of 1-2 days. Overall, the novel heat-health EWS demonstrated a high capacity to distinguish between warning and non-warning days at least 7 days in advance in majority of European regions (area under the ROC curve > 0.8). The system performed generally better in Southern Europe where the most of summer heat-related deaths occur.

Our study provides key information for public health agencies to activate heat-health action plans at the right time, accounting for the different vulnerability of different population subgroups and regional differences in vulnerability to heat across Europe.