South Korea recorded its highest average summertime temperature since such records began half a century ago, the weather agency said on Thursday, nearly 2 degrees Celsius higher than the historic average.

From June to August, the average temperature in the country was 25.6 degrees Celsius, the Korea Meteorological Administration said.

That is the highest figure since the agency set up nationwide observation posts to gather such data in 1973, it said, and is 1.9 degrees Celsius higher than the historical average for the summer period.

"From mid-June, temperatures remained higher than in previous years, even during the monsoon season when temperatures traditionally drop," the KMA said.

The head of the KMA, Jang Dong-un, said climate change was altering South Korea's weather patterns.

"We experienced heavy downpours during the monsoon season, and the prolonged heat wave and tropical nights caused significant discomfort and damage to the public," Jang said.

"As climate change is altering the climate characteristics of our country, the Korea Meteorological Administration will work hard to strengthen its monitoring and analysis capabilities for abnormal weather conditions."

Much of the world is enduring a blisteringly hot summer, with UN Secretary-General Antonio Guterres warning in July that humanity is suffering an "extreme heat epidemic" and calling for action to limit the impacts of heat waves intensified by climate change.