Introduction. The National Heat Wave Plan was established to mitigate the negative health impacts of heat waves. A simple method has been developed to provide policymakers with an initial estimate of a heat wave’s impact on mortality shortly after it occurs. We use this method to estimate the impact of the heat waves of 2010, 2011, and 2012. Methods. A heat wave is defined as a period during which the minimum and maximum temperatures, averaged over three days, simultaneously reach or exceed departmental alert thresholds. Excess mortality is estimated as the difference between observed mortality during the heat wave period and the three days following it, and a reference mortality rate calculated for the same period in previous years, up to five years prior to the heat wave. Results. The analysis focused on the heat waves of July 2010, August 2011, and August 2012, which affected 41 departments over the three summers. A small impact on mortality was observed: overall, in the departments affected by a heat wave, 84 excess deaths were estimated in 2010, 39 in 2011, while in 2012 there were 45 fewer deaths than expected. Discussion and Conclusion. The estimated low impacts can be explained in part by the implementation of rapid and effective preventive measures, and above all by the limited intensity and duration of the episodes studied, which cannot be considered true heat waves. (R.A.)