Last week Kuwait and the city of Basra in Iraq sweltered in 54C heat reported Dr Jeff Masters on the Weather Underground blog. At these temperatures, a major heat hazard is posed to human health.
The heat danger to human health was outlined by Steven Sherwood and Matthew Huber (2010) in the study: An adaptability limit to climate change due to heat stress which I reported on in May 2010: Scientists outline health limits of heat stress with Climate Change.