Seoul to hit 38 C on Wednesday as parts of greater Seoul area approach 40 C

Extreme heat will grip western parts of South Korea on Wednesday, with temperatures forecast to approach 40 degrees Celsius in some areas. Gimpo, Ansan, Hanam, Osan, Yeoju, Pyeongtaek and Yongin in Gyeonggi Province are expected to reach 39 C, while Seoul and Gwangju are forecast to hit 38 C.

The greater Seoul area, the Honam region and parts of the Yeongnam interior endured another tropical night Tuesday, with overnight temperatures staying dangerously high.

In Seoul — measured at the Korea Meteorological Administration's Jongno-gu observation station — the overnight low was 29.0 C, just short of the threshold for a so-called "super tropical night," defined as a night when temperatures do not fall below 30 C between 6:01 p.m. and 9 a.m. the following morning.

Dongjak-gu, where the KMA's Seoul office houses its observation equipment near Boramae Park, did cross that threshold, recording an overnight low above 30 C and officially experiencing a super tropical night.

The heat is being driven by a ridge of the North Pacific High sitting over the East Sea, which funnels easterly winds onto the Korean Peninsula. As the air crosses mountain ranges, it becomes hot and dry — a phenomenon known as the foehn effect.

As of 8 a.m. Wednesday, temperatures in major cities reflected the west-heavy heat pattern: Seoul and Incheon at 29.3 C, Busan at 28.6 C, Daejeon and Gwangju at 28.2 C, Daegu at 27.3 C, and Ulsan at 26.8 C.

Daytime highs across the country Wednesday are expected to range from 30 C to 38 C.

Seoul and Gwangju are forecast to reach 38 C, Daejeon 37 C, and Incheon and Daegu 36 C.

Busan and Ulsan will see relatively lower peaks, with highs of 34 C and 33 C, respectively.

Taebaek, a highland city in the Yeongdong area of Gangwon Province with an average elevation of 965 meters, is expected to stay below 30 C, with a forecast high of 29 C.

Scattered showers are possible Wednesday afternoon to evening along the western coast of South Chungcheong Province and North Jeolla Province and across the Honam region, with additional showers likely in Seoul, Incheon and southwestern Gyeonggi Province from late afternoon into the evening.

The showers are unlikely to provide meaningful relief. Temperatures may dip briefly while rain falls, but are expected to rebound quickly once the showers pass — raising humidity and making conditions feel more oppressive.

The heat wave is expected to persist for now.

The key variable is Typhoon Dolphin, the 13th named storm of the season. The KMA's latest forecast has the storm — which passed about 1,140 kilometers east of Okinawa, Japan, at 3 a.m. Wednesday — continuing westward toward Shanghai, China, and reaching waters about 530 kilometers southeast of Shanghai by 3 a.m. Monday.

Meteorological agencies in Japan and other countries in the region have issued broadly similar forecasts for Dolphin's track toward the seas southeast of Shanghai.

If the typhoon follows its projected path, it is not expected to break the heat wave on the Korean Peninsula.

It is also unlikely to ease the severe drought gripping southern South Korea. The latest medium-range forecast shows rain only for the Yeongdong area of Gangwon Province and Jeju on Sunday.

From Sunday through Liberation Day on Aug. 15, morning lows are forecast between 22 C and 27 C and afternoon highs between 29 C and 36 C — below the extreme heat threshold but still warmer than average for the season.