Climate change is likely to result in an increase in extreme weather events in the future. Anticipating these events requires the establishment of a system to manage the crisis and its consequences. Epidemiology guides prevention and public health response efforts by identifying at-risk populations, detecting health events, and quantifying the health impact. Epidemiological surveillance of heat waves falls within the formal framework of the National Heat Wave Plan, in close coordination with weather forecasts. Its objectives are to assess the health situation, issue alerts, and assist in adapting management measures as needed. It focuses on a limited number of indicators that can be monitored in near real-time using data from the Oscour® (Coordinated Emergency Surveillance Organization) and SOS Médecins (out-of-hours primary care) networks, as well as recorded deaths. Additional epidemiological and sociological studies are needed to help identify new forms of vulnerability and the necessary adaptations that will ensure the effectiveness of prevention and management measures in the future. The variety of scenarios regarding the consequences of extreme weather events (storms, floods) points toward reactive monitoring, which adapts to specific conditions and can be rapidly scaled up for a particular event or population. A representative and comprehensive assessment of health impacts requires preparing a combination of healthcare utilization data (Oscour®, health insurance data) and cross-sectional or cohort surveys that allow for the precise collection of information and the tracking of health outcomes at the individual level. To this end, epidemiologists must be integrated into organizations managing the crisis and its health consequences from the planning phase onward. In any case, the necessary rigor and optimization must not hinder the flexibility and adaptability of surveillance systems, so that they can adapt at any time to changes in the situation and learn from successive feedback. (RA)