Chae Young-sun, a 69-year-old retired government employee living in the South Korean city of Gwangju, has stopped taking daily walks since a searing heatwave began gripping most parts of the country more than a month ago. “I’m worried about my health because it’s simply too hot to go for a walk,” he said. “Yesterday afternoon, I finally summoned the courage to take a short walk around my neighbourhood. Even though I stayed under the awnings of a market, I was sweating profusely and had to seek...