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'Higher than average' chance of heat waves expected this summer due to rapid decline of Arctic ice

Published: 27 May. 2026, 21:01

A child frolics in a water fountain in central Seoul on May 25. [NEWS1]

The upcoming summer might bring an onslaught of muggy, sticky and suffocating days and nights, along with a greater risk of heat waves and heat-related illnesses, because the Arctic sea ice is melting, according to a meteorological expert on Wednesday.

“This year is expected to bring a hot and humid summer,” said Prof. Lee Myung-In of Ulsan National Institute of Science and Technology and chief of the heat wave research center under the National Institute of Meteorological Sciences.

“The chances of heat waves and tropical nights are higher than average, and the warning signs this year are unlike anything we’ve seen before,” Lee said.

The warning signs Lee referred to were the rapid decline of Arctic sea ice and unusually warm waters in the North Pacific. The size of Arctic sea ice this spring fell to its lowest level since satellite observations began, and the trend is highly likely to persist through June.

“If positive Arctic oscillation conditions develop due to shrinking Arctic ice, high-pressure systems can become stalled over the mid-latitudes,” Lee said. “That pattern fueled severe heat waves in both 1994 and 2018, and it could once again increase the likelihood of extreme heat across the mid-latitude region this year.”

Sea surface temperature differences in April [JOONGANG ILBO]

The Arctic oscillation refers to periodic fluctuations in the strength of the atmospheric circulation surrounding the Arctic. During its positive phase, cold Arctic air remains trapped near the pole rather than descending into mid-latitude regions, allowing temperatures over the Korean Peninsula to rise.

Another major factor is the abnormally high seawater temperature in the North Pacific.

Since the early 2020s, the region has remained persistently warmer than average at near-record levels. Warmer North Pacific waters tend to funnel hot air and moisture toward the Korean Peninsula, increasing the likelihood of sweltering, sauna-like conditions.

“The reason humid heat and tropical nights have become more frequent in recent years is that sea temperatures in the North Pacific have significantly increased,” Lee said. “And because those trends are continuing this year, the likelihood of heat waves and tropical nights has grown even higher.”

Still, forecasters say a developing El Niño — a climate pattern marked by warmer-than-average sea surface temperatures in the eastern Pacific — could remain a variable this summer.

Summer cooling appliances are on sale at an electronics store in Seoul on May 24. [YONHAP]

An early transition into El Niño conditions, along with fluctuations in North Atlantic sea temperatures, could alter summer temperature and rainfall patterns in Korea, according to Lee.

Rising temperatures, combined with higher humidity, also heighten the risk of heat-related illnesses.

Humidity pushes apparent temperatures even higher. The apparent temperature refers to how hot or cold it actually feels to the human body. With nighttime temperatures that may remain elevated, it could lead to conditions in which heat waves and tropical nights occur simultaneously.

Workers carry out outdoor construction work in Seoul during a heat wave in July, 2025. [YONHAP]

The number of days experiencing both heat waves and tropical nights increased by 4.3 percent every decade between 1975 and last year, according to an analysis by the heat wave research center.

Heat-related illness was more common among men than among women. Heat-related illnesses occurred up to seven times more often outdoors than indoors.

In response, the Korea Meteorological Administration is introducing its first-ever extreme heat emergency warning and tropical night advisory system this year in preparation for what could be a record-breaking summer.

“When high temperatures continue day and night, they can inflict fatal damage on the human body,” Lee said. “That is why weather advisories, forecasts and corresponding response measures are critically important.”

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.
BY CHON KWON-PIL [[email protected]]