A decade-long study in 2010 by the US Centres for Disease Control and Prevention recorded 8,081 heat related deaths across America, with a third of victims aged 65 and above. A heatwave in France in 2003 resulted in 15,000 deaths in little more than a fortnight. Most victims were elderly or overweight. In March, a young Australian soldier died days after collapsing during a training exercise in Darwin, one of the country’s hottest cities. Dehydration adds to heat stress and risk of serious injury, so staying hydrated offers some protection but cannot guard against overheating. Doctors said cooling the body with ice packs or cold water was an effective way to reduce core temperature during and after a workout.