Yangsan hits 40 degrees for five straight days as heat wave grips South Gyeongsang
Winds are expected to shift from westerly to easterly from Monday, and the extreme heat that has been concentrated in South Gyeongsang is forecast to spread nationwide, including to the greater Seoul area.
People cool off at a fountain in Yangsan, South Gyeongsang, on July 31.YONHAP
A record-breaking heat wave is gripping inland South Gyeongsang, with Yangsan becoming the first place in Korean weather-observation history to top 40 degrees Celsius (104 degrees Fahrenheit) for five straight days on Sunday.
Yangsan, a city bordering Busan to the south and Ulsan to the northeast, recorded 40.3 degrees Celsius at 11:47 a.m. on Sunday, according to the Korea Meteorological Administration (KMA). Temperatures had climbed to 40.9 degrees Celsius by noon.
The city has topped 40 degrees Celsius every day since Wednesday, setting an unprecedented record in Korea's 122-year-history of weather observation.
Daytime highs reached 39 degrees Celsius in Gimhae, Changwon, Miryang and Jinju cities and Haman, Changnyeong, Uiryeong and Hapcheon counties — all in South Gyeongsang — on the same day.
Nationwide daytime highs range from 33 to 39 degrees Celsius. A critical heat wave warning — the newest and highest tier of Korea's heat alert system — was issued for parts of South Jeolla and South Gyeongsang.
The KMA attributed the extreme heat in Yangsan and other parts of inland South Gyeongsang to a combination of overlapping weather conditions. In the lower and middle atmosphere, the hot and humid North Pacific High remained close to the Korean Peninsula. Along the edge of this high-pressure system, warm, moisture-laden winds continued to flow into the region from the west and northwest.
A water truck sprays water onto a road in Yangsan, South Gyeongsang, on July 31,YONHAP
After the summer monsoon ended, another high-pressure system known as the Tibetan High expanded eastward from the Tibetan Plateau into the upper atmosphere over the peninsula. While the North Pacific High sits closer to the Earth's surface, the Tibetan High forms much higher in the atmosphere. Together, the two systems effectively trapped the Korean Peninsula between layers of high pressure.
High-pressure systems cause air to sink. As the air descends, it is compressed and warms, a process known as adiabatic warming. With high pressure both above and below, the warming effect became even stronger while cloud formation was suppressed, allowing more sunlight to heat the ground.
The heat was further intensified by the foehn effect, which is a weather process that makes the downwind side of a mountain much warmer and drier than the upwind side. As the westerly and northwesterly winds crossed mountain ranges such as the Yeongnam Alps, the moist air cooled as it rose, causing water vapor to condense and fall out. After crossing the mountains, the now-drier air descended the eastern slopes, where it was compressed and warmed rapidly. By the time it reached lower elevations, it had become significantly hotter and drier, driving temperatures even higher in places such as Yangsan.
As the now-dry air descends the opposite slope, the temperature rises by roughly 1 degree for every 100 meters (328 feet), which is why areas on the leeward side of mountains become hot and dry.
Strong sunlight under clear skies also helped bake inland South Gyeongsang. Yangsan's solar radiation in July totaled 582.49 megajoules per square meter, about 36 percent higher than the normal 428.7 megajoules. A dry spell during the monsoon season, which left the ground parched, also fueled the heat: soil moisture at an agricultural observatory near Yangsan measured just 26.3 percent of normal. When soil lacks moisture, more of the sun's energy goes toward heating the ground and air instead of evaporating water.
The dried and cracked bed of Oryong Reservoir is exposed in Ulsan, on July 31.YONHAP
Yangsan in particular sits in a basin ringed by high mountains, including Mount Gaji, Sinbul, Maebong, Cheonseong and Geumjeong. Surface winds converge there, and heat carried in over the mountains has struggled to escape. Because the heat hasn't sufficiently dissipated overnight, morning temperatures have also been climbing.
With these conditions repeating, Yangsan hit 40.3 degrees Celsius on Wednesday and Thursday, 41.4 degrees Celsius on Friday, 41.6 degrees Celsius on Saturday and 40 degrees Celsius on Sunday.
The heat wave is expected to continue for now. On Monday, morning lows were forecast at 23 to 27 degrees Celsius and daytime highs at 32 to 38 degrees Celsius. The maximum perceived temperature in most parts of the country was expected to climb to around 35 degrees Celsius, with tropical nights common in many areas.
Temperatures typically peak in early to mid-August. With clear skies expected to continue for the time being, this week is likely to mark the peak of the heat wave if current forecasts hold.
Starting Monday, winds are expected to shift from westerly to easterly, and the extreme heat that has been concentrated in South Gyeongsang is forecast to spread nationwide, including to the greater Seoul area. Seoul's daytime high is expected to reach 37 degrees Celsius on Thursday. Heat around 35 degrees Celsius is expected to continue into next week as well, though temperatures are forecast to ease somewhat compared to this week.
Typhoon Dolphin, the 13th typhoon of the season and currently maintaining strong intensity, could intensify the easterly winds and worsen the heat in western regions.
"Moist easterly winds crossing the Taebaek Mountains could heat up further and intensify the heat wave in western regions," said Kang Nam-young, a professor of geography at Kyungpook National University.
Heat haze rises from an asphalt road in Daegu on July 31.NEWS1
As the heat wave drags on, health impacts are also mounting. A total of 1,781 people had suffered heat-related illnesses as of Friday, including an estimated 13 deaths, according to the Korea Disease Control and Prevention Agency.
"Older adults are especially vulnerable to heat-related illness because their sweat gland function and blood vessel response decline, and they also feel thirst later than others," Kim June-sung, a professor of emergency medicine at Asan Medical Center, said. "Even after recovering from a heat-related illness, lasting damage to the brain and heart can remain."
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.
