Periods of extreme heat can lead to heat-related illnesses, the worsening of pre-existing conditions, or hyperthermia. Implemented annually, the national prevention and crisis management plan aimed at reducing the health effects of a heat wave includes three progressive alert levels, based on minimum and maximum biometeorological indices (IBM) and on alert thresholds specific to each department: - "seasonal watch," triggered automatically from June 1 to August 31, 2012, - "Warning and Action" (Miga), triggered by departmental prefects based on meteorological and health risk assessments conducted by the InVS in collaboration with Météo France, - "Maximum Mobilization," corresponding to an exceptional situation extending beyond the health sector and requiring the mobilization of all relevant stakeholders. This level is triggered by the Prime Minister.