Seoul set to reach 39 degrees Celsius while Tokyo stays cool

Seoul is bracing for a high of 39 degrees Celsius (102.2 degrees Fahrenheit) on Wednesday, as Tokyo — normally one of Asia’s hottest cities in the summer — stays under 30 degrees Celsius in a striking reversal of the two’s typical summer weather patterns.

Seoul reached 35.4 degrees Celsius as of noon on Wednesday, with the city’s daytime high expected to climb to 39 degrees Celsius, according to the Korea Meteorological Administration (KMA). 

All of Seoul remains under a heat wave emergency warning, the highest level in Korea’s three-tier heat wave alert system.

The agency also issued heat wave emergency warnings on Wednesday for Gwangmyeong, Yeoncheon, Pocheon, Namyangju, Uiwang, and Hwaseong cities and Yangpyeong and Gapyeong counties in Gyeonggi; Cheongyang County in South Chungcheong; and southern Incheon. This marked the first time that a heat wave emergency warning had been issued anywhere in Chungcheong.

Including areas that had already had such measures in effect, 20 of the 46 land-based weather advisory zones across the greater Seoul area are now under a heat wave emergency warning. The remaining 26 zones issued a standard heat wave warning.

“Easterly winds will keep flowing into the greater Seoul area for the time being and push temperatures sharply higher,” a KMA official said. “Many areas will see highs of 39 degrees Celsius or above, bringing life-threatening levels of extreme heat.”

Tokyo, by contrast, is seeing weaker heat than usual for this time of year. According to the World Weather Information Service, the city is expected to stay cloudy on Wednesday, with a daytime high of just 28 degrees Celsius — more than 10 degrees cooler than Seoul.

Tokyo has traditionally been one of the region’s hottest cities, with an average August temperature of 31.3 degrees Celsius, higher than Seoul’s 30 degrees. But in recent years, Tokyo has seen a stretch of cool, autumn-like weather, with daytime highs staying below 30 degrees.

The sharp divergence between the two stems largely from surrounding pressure systems and wind patterns. In Seoul’s case, two high-pressure systems — the North Pacific High and the Tibetan High — have formed a heat dome over the region. Hot easterly winds, warmed as they cross the Taebaek Mountains, have only driven temperatures higher.

Tokyo, meanwhile, has been under the influence of the Okhotsk High, positioned northeast of Hokkaido, which has been pushing in a cold, damp northeasterly wind. This has caused Tokyo’s temperatures to drop sharply, as if the city skipped summer entirely and moved straight into early fall. Western Japan, including Kyushu, is seeing a very different picture, however, with extreme heat nearing 40 degrees Celsius, highlighting a stark east-west temperature divide within Japan.

Starting Thursday, Tokyo’s daytime temperatures are expected to climb back above 30 degrees Celsius. But Seoul is forecast to remain locked in extreme heat of up to 39 degrees Celsius through Thursday and Friday, so the heat gap between the two cities will likely persist for now.

BY CHON KWON-PIL [lee.jian@joongang.co.kr]