At least 19 people died as South Korea recorded its highest temperature ever and president Lee Jae Myung called the ongoing heatwave a national disaster.

Speaking at a cabinet meeting, Mr Lee ordered officials to take necessary measures to protect the daily lives of people and inspect power systems as demand for air conditioning surges.

Seoul was also forced to issue the first severe heat warning in its history.

“An even greater concern is that abnormal weather conditions make ⁠it highly likely that extreme weather will continue for a considerable period,” he said, calling for a major redesign of the disaster response system to cope with the hazardous conditions.

“We need to make efforts for a fundamental overhaul of the national crisis system, since this extreme weather is becoming normal,” he said earlier.

The warning took effect across the capital, home to more than nine million people, at 11am on Tuesday local time, a day after it was first issued for parts of the city and the surrounding province of Gyeonggi.

Seoul was forecast to reach 38C on Tuesday and 37C for the three days after.

More than 2,000 people have been treated for heat-related illnesses since May, according to the Korea Disease Control and Prevention Agency.

Two elderly men died while working outdoors on Sunday. One was found collapsed in a greenhouse near Seoul and the other in the southern port city of Busan.

The heat has been concentrated in the southeast, where Yangsan, an inland city in South Gyeongsang province, reached 42.5C on Sunday, the highest temperature measured in 122 years of observation in South Korea.

Goryeong, also in the southeast, reached 41.2C on Monday, and several places passed 41C. One district of Seoul recorded 39C.

The severe warning is part of a new system introduced on 1 June. It is triggered after a lesser warning runs for two days and the following day is forecast to feel like 38C or actual temperature crosses 39C.

By Monday, 217 of the country’s 235 land-based warning zones, or 92 per cent, were under some form of heat alert.

Forecasters attribute the heat to overlapping areas of high pressure sitting over the Korean peninsula under clear skies. The southeast is made hotter still by the foehn effect of air crossing a mountain range, warming up and drying as it descends the far side. The same mechanism is now pushing the heat west across the Taebaek and Sobaek ranges towards Seoul.

Read More: South Korean president declares heatwaves ‘national disaster’