Scorching heat and heavy rain hit Korea as summer swings between extremes

Heavy rain returned across Korea early Monday, following a weekend of extreme weather marked by scorching heat and heavy rain alerts across the country.

Pedestrians with umbrellas cross Sejong-daero, a street in Jongno District, central Seoul, on June 16 as rain pelts the country. [YONHAP]

Heavy rain returned across Korea early Monday, following a weekend of extreme weather marked by scorching heat and heavy rain alerts across the country.

Inland areas experienced searing temperatures during the day on Sunday, with the mercury rising well above 30 degrees Celsius (86 degrees Fahrenheit), according to the Korea Meteorological Administration (KMA).

This summer’s first heat wave advisories were issued in several Gyeonggi regions, including Pocheon, Gapyeong, Paju, Anseong, Yeoju and Yangpyeong. It came five days later than last year, when the first heat wave alert was issued in the Gyeongsang region on June 10.

A heat wave advisory is issued when the perceived temperature is expected to exceed 33 degrees for at least two consecutive days.

On Sunday in Seoul, the daytime high reached 33.2 degrees, more than 5 degrees above the seasonal average. The highest temperature nationwide was recorded in Buknae-myeon and Heungcheon-myeon in Yeoju, Gyeonggi, where the thermometer hit 34.8 degrees.

A pedestrian uses a bag to avoid the rain while walking near near Gwanghwamun Square on June 16. [YONHAP]

Daytime heat, nighttime downpours

While the intense heat was forecast to subside after sundown, the relief will be short-lived. The KMA warned of heavy showers starting Monday, with rainfall rates expected to reach around 30 millimeters (1.2 inches) per hour, raising the risk of flash floods and water damage.

Weather authorities issued preliminary heavy rain alerts for northern Gyeonggi and Ganghwa County in Incheon as of Sunday night. The wider Seoul metropolitan area is expected to receive between 20 and 60 millimeters of rain on Monday, with parts of northern Gyeonggi and Incheon potentially seeing over 80 millimeters.

The KMA emphasized the possibility of highly localized but intense rainfall in short bursts, warning that this could cause serious disruptions in a narrow area.

Jeju Island and parts of the southern region, which entered an early monsoon season last week, are also forecast to receive another bout of heavy rain between early morning and noon on Monday. In Busan, a sudden downpour dumped 61.2 millimeters of rain in just one hour around midnight Saturday, breaking the city’s previous hourly rainfall record for June.

“A significant amount of rain — more than 100 millimeters — already fell on southern areas and Jeju on Saturday,” a KMA official said. “Now, we’re expecting more intense and heavy rain. People should stay alert for flooding in low-lying areas, river overflows and swift currents.”

A heat haze caused by ground temperature rises above Yeoui-daero in Yeongdeungpo District, western Seoul, on June 15, as daytime temperatures in Seoul surpassed 30 degrees Celsius (86 degrees Fahrenheit). [YONHAP]

Unusually hot and stormy monsoon season

The KMA’s midrange forecast shows rain falling on and off through this weekend, with extreme heat and sudden downpours persisting across the country. Thunderstorms may also accompany these showers.

There is also a chance the monsoon season could begin earlier than usual in central Korea. Historically, the monsoon begins around June 23 in the south and June 25 in central regions.

Meteorologists are increasingly concerned that this summer’s monsoon will be marked by alternating bouts of intense rainfall and extreme heat — a volatile pattern that could trigger compound weather disasters.

After short but intense rainfall events, heat waves are expected to return quickly, creating highly unstable weather conditions.

The Japan Weather Association also warned that this year’s monsoon would likely bring “sudden downpours followed by extremely hot and sunny days, indicating a positive-phase monsoon pattern.”

Kim Hae-dong, a professor of environmental engineering at Keimyung University, explained the dynamics behind this trend.

“The ground is heating more than in the past, and hot, humid air is pushing in. That’s making the atmosphere highly unstable,” he said. “This year’s monsoon is likely to produce more intense rainfall in narrow zones.”

Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff. BY CHON KWON-PIL [kim.juyeon2@joongang.co.kr]