A heatwave in Europe during summer 2003 caused a significant increase in mortality, with over 70,000 additional deaths recorded across 16 European countries. The study analyzed daily mortality data from 1998–2002 to compare with 2003, revealing major distortions in age distribution and no harvesting effect in the months following August 2003. The excess mortality was particularly high in France, Italy, Spain, and Luxembourg, with some countries experiencing increases of over 14%. The mortality crisis peaked in late August, with some regions experiencing mortality rates twice the expected levels. The study highlights the difficulty in detecting the impact of global warming on public health, especially in aging populations. It emphasizes the need for centralized monitoring of daily deaths at an operational geographical scale to better detect and respond to excess mortality. The findings underscore the importance of public health preparedness for future heatwaves and climate-related health threats.A heatwave in Europe during summer 2003 caused a significant increase in mortality, with over 70,000 additional deaths recorded across 16 European countries. The study analyzed daily mortality data from 1998–2002 to compare with 2003, revealing major distortions in age distribution and no harvesting effect in the months following August 2003. The excess mortality was particularly high in France, Italy, Spain, and Luxembourg, with some countries experiencing increases of over 14%. The mortality crisis peaked in late August, with some regions experiencing mortality rates twice the expected levels. The study highlights the difficulty in detecting the impact of global warming on public health, especially in aging populations. It emphasizes the need for centralized monitoring of daily deaths at an operational geographical scale to better detect and respond to excess mortality. The findings underscore the importance of public health preparedness for future heatwaves and climate-related health threats.