South Korea’s capital broke a century-old weather record with the 26th so-called tropical night in a row, as the temperature stays above 25°C, according to official data released Friday.

“The cold air is not coming down from the north and as we are affected by the warmer side of the southwest, the temperature is continuously recording around 25°C or above,” Youn Ki-han, director at Seoul’s Meteorology Forecast Division, told AFP.

Much of the world is enduring a summer of extreme heat, with United Nations Secretary-General Antonio Guterres warning last month of an “extreme heat epidemic”, and calling for action to limit the impact of climate change.

Overnight temperatures in the South Korean capital Seoul have sizzled above 25°C for 26 days in a row, officials said, marking the longest streak since modern weather observation began in 1907.

The record ties one set in 2018, but the weather agency counts the most recent as the benchmark.

The intense heat in Seoul is expected to continue, according to Seoul’s Office of Meteorology, setting a record every day until next week.

The 25-degree-plus evenings are widely known as “tropical nights” in South Korea, and officials say such a long streak is unusual.

“Usually around this time the temperature drops in the morning and evening as the cold air comes down from the northwest, and the North Pacific high-pressure contracts, but currently we aren’t seeing any signs of that yet,” said Youn.

South Korea’s second-largest city Busan, meanwhile, logged its 22nd consecutive tropical night, marking its longest streak since records began in 1904.

According to the International Institute for Environment and Development (IIED), the number of days with temperatures reaching 35°C in the world’s largest capital cities has surged by 52% over the past 30 years.

In 2018 alone, Seoul experienced 21 days with temperatures over 35°C — more than the previous 10 years combined.

“In just one generation, there’s been an alarming increase,” said Dr Tucker Landesman, a senior researcher at IIED.

Climate activists in South Korea are calling for more government action.

“There’s no chance that this will get better and it’s bound to get worse,” Youn Se-jong, an environmental lawyer, told AFP. “Strengthening the goal of reducing greenhouse gas emissions should be the priority,” he added.