Korea is currently experiencing one of the most extreme heat waves since weather records began. On July 8, for the first time in early July, temperatures in Gwangmyeong, Paju, and Anseong in Gyeonggi Province surpassed 40 Celsius degrees.

Seoul also saw its temperature rise to 37.8 degrees, the highest ever recorded in early July. The scorching heat that had persisted along the east coast was carried westward across the Baekdudaegan mountain range by easterly winds.

According to the Korea Meteorological Administration (KMA), at 3:24 p.m., the temperature in Gwangtan-myeon, Paju, reached 40.1 degrees, followed by 40.2 degrees in Cheolsan-dong, Gwangmyeong, at 3:42 p.m. At 5:06 p.m., the temperature in Ihyeon-ri, Yangseong-myeon, Anseong, also hit 40.1 degrees. This is the first time since August 4 of last year that any part of Korea has seen temperatures exceed 40 degrees, and it marks the first time such extreme heat has been recorded in early July rather than mid-summer.

Several areas broke their previous early July temperature records. At 3:09 p.m., Seoul’s temperature reached 37.8 degrees, the highest ever recorded in the capital for early July since measurements began. The previous record was 36.8 degrees, set on July 9, 1939. Since weather observation began in 1908, this marks the highest early July temperature in 117 years.

Other cities also set new records for early July: Suwon (36.7 degrees), Cheongju (36.3 degrees), Daejeon (36.3 degrees), Seosan (36.5 degrees), Paju (34.9 degrees), and Bukchuncheon (37.2 degrees). Most of Korea’s western regions, under heat wave advisories, experienced sweltering conditions, with apparent temperatures ranging from 30 to 38 degrees.

The KMA forecast that easterly winds blowing along the edge of a high-pressure system located in the northern East Sea are likely to strengthen heatwave advisories, particularly in western regions such as Incheon and western Gyeonggi Province.

On July 7, Seoul issued its first heat wave warning of the year. Tropical nights, where temperatures do not drop below 25 degrees overnight, were also observed in Seoul and parts of the Chungcheong and Jeolla inland and west coast regions.

Until July 6, before the easterly winds arrived, record-breaking heat had been concentrated in the Yeongdong region, including Gangneung, Donghae, and Uljin. In Gangneung, where tropical nights have continued since June 29 for eight consecutive days, there were frequent occurrences of super tropical nights, when the overnight low stays above 30 degrees. With the arrival of cooler sea breezes from July 7, afternoon temperatures dropped to 28.5 degrees in Gangneung, 26.2 degrees in Donghae, and 28.6 degrees in Uljin.

The stark difference in temperatures between the east and west of the Taebaek Mountains is due to the “foehn effect,” a phenomenon where air heats up as it descends down a mountain slope. When westerly winds blow, coastal areas along the West Sea remain relatively cool due to sea breezes, while the east coast, where the air descends dry and hot over the mountains, becomes extremely hot. When easterly winds blow, the pattern reverses. The heatwave is expected to last at least until July 16. The easterly winds that brought heat to the west are forecast to subside around July 11. After that, as southwesterly winds flow between an approaching low-pressure system from the northwest and a high-pressure system to the south, Korea is expected to experience hot, humid, and muggy weather. During that period, the eastern side of the Taebaek Mountains may once again become extremely hot. The KMA said, “In areas where showers occur, temperatures may temporarily drop, but once the rain ends, heat and humidity will quickly return, making it feel even hotter.”