South Korea registered its highest temperature on Sunday since records began more than a century ago, according to the state weather agency. The southeastern city of Yangsan saw the temperature reach 42.5C at 1:26 pm (0426 GMT), the Korea Meteorological Administration said on its website. Much of South Korea has been placed under heat warnings, with many cities seeing temperatures climb into the high 30C. More than 20 localities were under emergency heatwave alerts on Sunday, a new warning category introduced this year to better address rising temperatures. A heatwave day is defined as one with a maximum temperature of at least 33C, while a tropical night is one when the overnight low remains 25C or above.