Heat wave doesn’t have a uniform definition across the world, as the specific weather conditions and the reaction of the socio-environmental system on them are not identical across time and space. According to the World Meteorological Organization (WMO), there is a significant warming of the air, a period characterized by abnormally high temperature or very hot air invasion. WMO advised though, that there should be a standard definition of what a heat wave means in terms of maximum and minimum temperatures in a given area or region (WMO 2010).
French climatologists define a heat wave as a period when the maximum daily temperature exceeds 5 ° C normal for at least five consecutive days. This definition corresponds to the STARDEX index used in most simulations for France and Europe. (Météo-France 2014)
In France, the period of intense heat which can lead to a heat wave generally runs from July 15 to August 15, sometimes from the end of June. Separate episodes of heat can occur not necessarily during this period. However before June 15 or after August 15, hot days only very rarely can be qualified as a heat wave. The nights are long enough so that the temperature drops well before dawn. (Météo-France, 2014)
Climate change and its consequences affect a set of natural systems and socio- economic sectors: agriculture and forestry, marine and coastal ecosystems, plant and animal species, the quality and availability of water resources, human health and security, economic and social activities. In the case of the increased frequency and intensity of extreme events, like heat waves there’s a risk of extreme impacts on human society and environment. These supposed impacts depend not only on the very heat event (hazard), but also there is a high confidence that the risk depends on exposure and vulnerability of the societies and socio-ecological systems to the hazard (Cardona et al., 2012).
When the risk is “realized”, or rather left unmanaged, it may result in a disaster, which in it is turn is associated with differing levels and types of adverse effects: from hardly noticeable to catastrophic levels (Cardona et al 2012). These effects, or impacts, manifest themselves as human and financial losses, loss of life, security, health and loss of assets. Moreover, there’s a high confidence that cumulative effects of several small disasters may seriously deteriorate the capacities of a socio-environmental system to cope with future disasters (Cardona et al., 2012).