Heat waves are the deadliest of weather phenomena in the developed world, killing more people than blizzards, storms or floods. Their lethality is determined by many factors - the number of days of prolonged hot weather, the humidity in the air, and the number of respites when the minimum temperature drops down to a tolerable level. Yet there are also social factors.

Through analysing the number of excess deaths for certain causes of deaths (such as hyperthermia, strokes and dehydration) compared with figures from other time periods, it is possible to calculate a death toll. Some of the worst heatwaves in history have occured in France in August 2003 (14,000 estimated dead), Greece in July 1987 (2,000 dead), Belgium in July 1994 (1,226 dead), New York in July 1972 (891 dead), and Chicago in July 1996 (739 dead). The urban sociology of Chicago which led to the deaths in 1996 is explained quite well in the book Heatwave - A Social Autopsy of Disaster by Eric Klinenberg.

Since heatwaves cause no physical damage (except if power systems overload because everybody has their air conditioner switched on), there is little public attention of the loss of life. Also, victims of heatwaves tend to be elderly people with little social networks. Their deaths are written off as inevitable, even if with a little bit of intervention they could have been saved. It is too easy for a government to blame old age or just the weather for heatwave deaths, rather than spend money on better aged care programmes, or point the finger at the voting public.

Ways how governments can limit the medical impact of heatwaves include:

  • ensuring hospitals are adequately staffed (many doctors in France in August 2003 were spending their holiday credits at the beach, accumulated thanks to the 35 hour week).
  • ensuring buildings are built to insulate against heat, are appropriately air conditioned, or at least are well-ventilated.
  • promoting prevention, such as the regular drinking of fluids.
  • opening air conditioned public spaces to the public.
  • enhancing social capital, so that people actively look after each other, particularly those without family or friends. Many elderly people died in the Chicago heatwave because out of a fear of burglary they did not adequately ventilate their apartments.