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Heatwaves will become longer, more frequent: Expert

Published: 26 May. 2025, 19:07 Updated: 26 May. 2025, 19:38

Citizens cool themselves with portable electric fans during an outdoor festival on May 22 in central Seoul. [YONHAP]

Extreme heatwaves are getting longer and becoming more frequent. And yes, this summer may see another one.

“The extreme heatwave that hit Korea in the summer of 1994 was said to come only once in a hundred years — yet that record was broken in just 30 years,” said Lee Myong-in, head of the Korea Meteorological Administration’s (KMA) Heatwave Research Center and a professor at the Ulsan National Institute of Science and Technology (Unist), said Monday.

“While global temperatures are rising linearly, heatwaves are increasing exponentially,” he said, stressing that this summer could also see longer and more intense heatwaves and tropical nights than usual.

Indeed, heatwaves in Korea have been arriving faster and lasting longer. According to the KMA’s heatwave white paper, the first heatwave of the summer arrived six to seven days earlier in the 2010s than in the 1990s, while the last one was delayed by one to two days, meaning more days of sweltering weather overall.

Heatwaves typically begin in early summer when migratory anticyclone — high-pressure areas whose center keeps changing — and strong sunlight cause temperatures to rise. In June, the sensible temperature — the temperature that people actually feel, as opposed to the numbers they see on the forecast — typically hovers around 27 to 28 degrees Celsius (80.6 to 82.4 degrees Fahrenheit), increasing to 30 degrees in July and exceeding 32 degrees in August, when the heat is at its peak.

Due to global warming, the number of heatwave days has increased in months with less rainfall such as June and August. Rising sea surface temperatures have also increased humidity levels, further driving up the sensible temperature — a key reason the heat now feels more unbearable.

Citizens cool themselves with portable electric fans during an outdoor festival on May 26 in central Seoul. [NEWS1]

Heat dome blankets the already hot summer

Climatologists say climate change and the emergence of “towering high-pressure systems” are the primary culprits behind longer, more severe heatwaves and tropical nights.

When the North Pacific high-pressure system at the lower atmosphere and the Tibetan high-pressure system at the upper atmosphere expand simultaneously, they form a tall, layered high-pressure zone over the Korean Peninsula. This phenomenon, known as a “heat dome,” traps heat like a thick quilt, extending the duration of heatwaves.

Last year, the heat dome led to prolonged scorching temperatures and tropical nights into the fall. Korea saw 30.1 days of heatwaves and 20.1 tropical nights — the second and first highest numbers on record, respectively.

A customer looks at air conditioners on display at a retail store in Seoul on May 25 amid hot weathers continuing through the month. [YONHAP]

Bracing for a very imminent summer

Korea has already experienced unseasonably hot weather since May, but the KMA is forecasting higher-than-average temperatures and more heatwave days this summer.

“Due to rising global temperatures and high sea surface temperatures in the northwestern Pacific, we could see a significant increase in the number of heatwave days compared to the average,” Professor Lee warned.

A repeat of last year’s heat dome could result in prolonged heatwaves and tropical nights again this year. Those above the age of 50 and outdoor workers are particularly vulnerable to heat-related illnesses. In response, Gyeonggi this year introduced a climate insurance policy that provides a payout of 100,000 won ($73) upon diagnosis of a heat-related illness.

“Given the high probability that last year’s atmospheric conditions will repeat themselves this year also, we must prepare for heatwaves and tropical nights that could last into the fall,” said Kim Hae-dong, an environmental engineering professor at Keimyung University.

Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff.
BY CHON KWON-PIL [[email protected]]