Heat waves can be deadly and are the leading urban environmental risk [Anderson and Bell, 2009;Guha-Sapir et al., 2010]. The most serious health conditions related to extended high temperatures are heat stroke and heat exhaustion. But these ailments tell only part of the story as most of those admitted to hospital during a heat wave arrive suffering from a wide range of indirect problems [Flynn et al., 2005], such as heart attacks [Madrigano et al., 2013], asthma and organ failure brought about by dehydration.Heat extremes occasionally cause large numbers of casualties leading to mortality rates that resemble epidemics [Gover, 1938]. Consider the impending risk of heat extremes on cities, a systematic method for assessing the risk of these extremes is proposed in this paper. The management of risk comes in several forms. For example, an understanding of the epidemiology of heat related illness is essential in developing strategies to reduce vulnerability of populations to temperature extremes. Impacts can be highly variable and depend on time of year, duration and intensity of the event, as well as aspects of demography and physical geography. For example, damaging heat impact often occurs at relatively low temperature or in pockets of the city with poor ventilation or with microclimates brought on by the urban heat island effect.Additionally, experience has shown that heat related mortality and morbidity can be significantly reduced if citizens are warned and that the most vulnerable members of the population are supported [Sampson et al., 2013]. Reduction of casualties to acceptable levels of public health requires additional effort and expense [Lass et al., 2013]. This includes identifying the populations most at risk, developing an effective plan and appropriate equipment to support them and obtaining the correct trigger to instigate an intervention. Plans that have taken these factors into account show evidence of success [Kalkstein et al., 2011]. Elements of the organisation required are the focus of this paper. With a good assessment of risk, civic planning for building resilience to the risk of heat extremes can be prioritised as heat waves are expected to increase. Two major changes drive this: one climatological and the other demographic. Firstly, the intensity and duration of extreme will increase as the climate warms [Coumou and Rahmstorf, 2012; Coumou et al., 2013]. There is even the suggestion that temperature extremes are increasin