Why so hot, so soon? Sudden summer heat leaves residents, visitors seeking shelter

A man cools off by soaking his head in water at Daegu Stadium as the daytime high soars to 33.4 degrees Celsius, Tuesday. Yonhap

Wednesday wasn’t the best day to visit Seoul for Park Seo-kyung, a high school sophomore visiting from Goheung, South Jeolla Province, on a school trip.

“We arrived in Seoul yesterday, and it’s so much more humid and hot compared to where I'm from,” she told The Korea Times. “I wanted to spend more time outdoors since we came all the way here, but the heat makes it tough.”

Even long-time Seoul residents found it to be a sweltering day.

Morning temperatures on Wednesday hit 23 degrees Celsius, the highest May morning low ever recorded in the capital since modern weather observations began in 1907.

At around 11 a.m. near Gwanghwamun, a public square located in Jongno District, temperatures hovered at 26.6 degrees Celsius, six degrees higher than the previous day. Cheonggye Stream, usually bustling with residents and tourists enjoying a morning stroll, was nearly empty.

Cheonggye Stream lies empty as an unexpected heat wave hits Seoul, Wednesday. Korea Times photo by Park Ung

One of the few braving the heat was Kim Si-yoo, a 21-year-old student who had just arrived from Boston, wearing long sleeves and pants, unprepared for Korea's sudden summer-like weather.

“I just got here yesterday, and it’s still pretty chilly in Boston. But here, it’s already really hot,” Kim said. “It feels like summer came too quickly. I’m having a hard time adjusting.”

But while a few souls braved the heat, many others sought relief indoors. In search of comfort, people flocked to cafes, malls and bookstores.

“I was planning to visit the National Museum of Modern and Contemporary Art during lunch today,” said Baek Chang-hyun, a 65-year-old cultural planning agency worker, at Kyobo Book Centre in Gwanghwamun, the largest bookstore in the country.

“But it felt way too hot to walk all the way there, so I came here instead,” he said. “We turned on the air conditioning at the office starting today. In recent years, the weather has been so hot that even a day like this just feels normal now.”

Wednesday’s heat was largely driven by a high-pressure system located off the eastern coast of Japan, which brought a continuous inflow of hot and humid southerly winds.

Through Sunday, the hot weather is likely to continue under mostly cloudy skies nationwide, with morning lows ranging from 12 to 19 degrees and daytime highs registering between 19 degrees and 27 degrees, according to the Korea Meteorological Administration (KMA).

Summers in Korea are becoming increasingly hotter, driven by factors such as climate change and the urban heat island effect — a phenomenon where cities become hotter than surrounding rural areas due to concrete, asphalt and reduced greenery.

According to the Ministry of Environment, Korea’s annual average temperature rose by approximately 1.6 degrees Celsius from 1912 to 2020, significantly higher than the global average increase of 1.09 degrees.

Last summer, the national average temperature hit 25.6 degrees Celsius, the highest since 1973, according to the KMA. The number of tropical nights, when temperatures remain above 25 degrees overnight, also reached a record high, averaging 20.2 days nationwide.

A cooling fog system sprays mist at a city bus stop in Gangneung, Gangwon Province, to help people beat the heat as temperatures climbed above 30 degrees Celsius, Tuesday. Yonhap

The rise in temperatures in recent years has driven up sales of summer-related products. During July and August last year, ice cream sales saw sharp increases across major convenience store brands compared to the same period in 2023: up 17 percent at 7-Eleven, 19.5 percent at CU and 18.4 percent at GS25.

Sales of iced coffee have also increased.

Between June and August last year, iced coffee sales at CU rose by 30.5 percent compared to the same period the year before. In 2023, the convenience store chain also reported selling more than 20 million units of its 400-gram jumbo ice cups, designed for people to pour drinks into and enjoy them cold, within just two years of their launch.