South Korea broke a century-old weather record with the 26th so-called tropical night in a row -- when the temperature stays above 25 degrees Celsius, according to official data released Friday.

Much of the world is enduring a summer of extreme heat, with UN Secretary-General Antonio Guterres warning last month of an "extreme heat epidemic", and calling for action to limit the impact of heatwaves intensified by climate change.

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

The record ties a streak 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 Metrology, setting a new record every day until next week. (AFP)