Heat is a silent killer. When it gets too hot, the heart pumps faster, blood races and organs begin to fail. The stress overwhelms the body as it struggles to cool itself down. Internal temperatures rise from regular (37C) through feverish (38C) to deadly (40C).
Many people who spend most of their time outside, such as farmers, builders and the homeless, die outright from heatstroke. But far more lives are claimed by heart, lung and kidney disease made worse in hot weather. Research pegs the death toll from heat in Europe last summer at 61,672 people – more than a jumbo jet crashing out of the sky every day.
