We have evaluated the incoherencies and discrepancies of health messages given by various sources and critically assessed the efficacy of this advice by reviewing current evidence supporting these measures on the basis of observational studies and from the physiology of heat response. [...] Sport medicine, the military, and occupational health bodies have also produced guidelines, which are of particular interest given their emphasis on work in the heat, and on optimal clothing for the heat, which are of relevance beyond the realms of sport, work, and war. [...] From experimental studies on people in their 40s and 50s, it appears that healthy elderly may be able to attain levels of physiologic acclimatization close to younger counterparts, but lack of activity and lack of exposure to a range of temperatures may deprive them of the opportunity to effect this protective adaptation (Robinson et al., 1965). [...] Identifying those people for whom air-conditioning may be most advisable, as well as the optimal duration and intensity of cooling, may help in the prescription of air conditioning and avoidance of negative effects of its use in heat-vulnerable persons and for society as a whole. [...] Several sites discourage the use of electric appliances during heat waves to minimize heat and reduce the chance of blackouts, but only the Ontario Ministry of Health and Long- term Care suggests to use a fan instead of air conditioning to conserve energy, while many other sites caution against using a fan to substitute for air conditioning when the temperature is high because it is a less efficie