In the January 2009 heatwave, a prototype heatwave alert system had just been introduced, based on research identifying a threshold temperature above which excess mortality occurred in Melbourne, Australia. By the time of the January 2014 heat wave, the heat alert system had been considerably refined, based on further scientific work (2–4) and intense interactions between climate scientists and public health authorities. The excess mortality associated with the 2014 heat wave was substantially lower than in 2009, even though the 2014 heat wave lasted longer.