THAT'S THE WHY:Wildfires in Russia and a death at the world sauna championships have served as recent reminders in the news that the human body does not always fare that well at high temperatures.

Heat has also engulfed Moscow, where the death rate has reportedly doubled, and the sauna competition in Finland was called off after Russian competitor Vladimir Ladyzhenskiy died during an attempt to challenge the title.

More generally, it’s not unusual to read reports of fatalities during intense heatwaves in Europe and the US – so why is heat such a killer?

The biochemical reactions that run us tend to work well within a fairly narrow band of temperatures, and our bodies have various strategies to compensate if we start to stray outside that zone.

But in intense and prolonged heat, coping mechanisms such as sweating can become overwhelmed and the body becomes extremely hot.

Overheating can lead to rashes, muscle cramps, fainting and in severe cases heat stroke, a serious and potentially life-threatening condition where core body temperature goes above 40.6 degree celsius and kidney and brain function can be seriously compromised.

Rapid diagnosis and treatment of heat stroke is the key to a good outcome, highlights a 2004 review paper in AACN Clinical Issues: “The prognosis is optimal when [heat stroke] is diagnosed early and management with cooling measures and fluid resuscitation and electrolyte replacement begins promptly. The prognosis is poorest when treatment is delayed more than two hours.”