August 2003. The hottest month ever observed in France but also most fatal. During fifteen days, historical temperatures will cause a medical catastrophe without precedent. 14 802 direct victims of heat will be officially listed... But what did it occur during this August 2003? Could we envisage, avoid all these deaths? How intense heat can suddenly become a threat and endanger our health? How to protect and fight heat? "Alarm heat wave" proposes to answer these questions. Utilizing doctors, political leaders, meteorologists but also those which particularly suffered from the heat wave, the film revisits the key dates of the heat wave 2003 with the ambition to give us the keys to prevent that such a catastrophe does not reproduce.