This summer (June to August), the national average temperature ranked third highest on record, following last year and the year before. That means three straight years of heat waves.

The Korea Meteorological Administration said on the 3rd that this summer's national average temperature was tallied at 25.4 degrees. It was 1.7 degrees higher than the normal (the 1991–2020 average).

Since 1973, when the meteorological observation network was expanded nationwide, the summer average temperature was the third highest after 2025 (25.7 degrees) and 2024 (25.6 degrees).

Children play in the fountain at Gwanghwamun Square in Jongno-gu, Seoul, on the 23rd as a heat advisory is in effect across the city. /Courtesy of News1

Through June this year, a blocking phenomenon that prevented upper-atmosphere air from flowing west to east from the Barents Sea to northern Siberia brought frequent inflows of cold air into Korea, but from mid-July to early August, the North Pacific high and the Tibetan high overlapped to cover Korea, prolonging extreme heat.

In particular, as the "foehn phenomenon" overlapped, the temperature in Yangsan, South Gyeongsang, rose to 42.5 degrees on Aug. 2 this year. It broke the record for the highest temperature in the 122-year history of meteorological observation in the country.

The Korea Meteorological Administration explained that, as of August this year, based on 83 Automated Surface Observing System (ASOS) stations, there were 42 instances at 13 stations where the daily high reached at least 39 degrees, surpassing 2018 (38 instances) and marking the most since 2010.

Also, the number of heat wave days (days with a daily high of at least 33 degrees) this summer averaged 21.5 nationwide, more than double the normal (10.6 days). Tropical night days (days with a nightly low of at least 25 degrees) likewise averaged 18.2, about 2.8 times the normal (6.5 days).

The sea was hot as well. This summer, sea surface temperatures in waters around Korea averaged 24.3 degrees, the highest in the past 10 years (2017–2026). Second place was last year and the year before at 24.2 degrees.

Summer average temperatures continue to rise. According to the Korea Meteorological Administration, over the 53 years since 1973, the summer average temperature rose 0.28 degrees per decade, and the upward trend has accelerated in the past 10 years. Eight of the top 10 years for highest summer average temperatures have occurred since 2010.

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