Spring or summer? Korea’s April heat set to last another week

A child lies on the ground near a water play area of Yeouido Hangang Park in Seoul on Sunday. Yonhap

Unseasonably hot, summer-like weather has swept across South Korea in mid-April, with daytime temperatures nearing 30 degrees Celsius and breaking records in several regions. Weather officials say the heat, driven by warm and humid southeasterly winds, is expected to persist for about a week, raising concerns that spring heat is becoming a “new normal” due to climate change.

According to the Korea Meteorological Administration on April 14, temperatures in Cheongpyeong, Gyeonggi Province, reached 29.7 degrees Celsius at around 3 p.m. the previous day. Around the same time, Seoul recorded 27.4 degrees, the highest so far this year.

The figure was the highest temperature ever recorded on that date in Seoul since weather observations began in 1907. It was about 10 degrees higher than the seasonal average high of 17.3 degrees Celsius for the period between 1991 and 2020. On April 14, Seoul again saw unusually high temperatures of 27.8 degrees at 3 p.m., the second-highest on record for the date, following 2024.

Similar record-breaking highs were reported nationwide, including in Wonju, Gangwon Province, at 28.1 degrees, Daejeon at 28.5 degrees, Gwangju at 29.1 degrees and Busan at 25.9 degrees. The heat was not limited to southern regions, with elevated temperatures also recorded in the Seoul metropolitan area and central regions.

Weather officials said the main driver of the early heat was warm and humid southeasterly winds, formed by a specific pressure pattern around the Korean Peninsula. A high-pressure system in the north and a low-pressure system moving quickly from west to east in the south have combined to push hot air toward the peninsula.

“This is similar to hot air blowing from a heater,” officials said, describing how the winds carry heat from the Pacific region toward Korea.

The situation has been worsened by a slow-moving high-pressure system acting like a lid, trapping warm air over the peninsula. Clear skies and weak winds have allowed sunlight to further heat the surface, while rapid cooling at night has led to daily temperature gaps exceeding 15 degrees Celsius.

Through April 20, average daytime highs are expected to range between 17 and 26 degrees Celsius, comparable to late May conditions. Daily highs this week are forecast to range from 15 to 28 degrees on April 14, 14 to 25 degrees on April 15 and 16, and 16 to 21 degrees on April 17 — about 5 to 10 degrees above seasonal norms.

In contrast, eastern coastal areas such as Gangwon and North Gyeongsang provinces are expected to remain relatively cool, with highs around 15 degrees due to easterly winds from the East Sea. Rain is forecast for Jeju Island and southern coastal areas through April 15 as low-pressure systems pass through.

Experts say the trend of warmer springs in Korea is likely to intensify. In a recent climate report covering 113 years from 1912 to 2024, the weather agency said the average spring temperature over the past decade was 13.6 degrees Celsius, up 1.9 degrees from the long-term average of 11.7 degrees. This increase is larger than the rise seen in summer at 1.5 degrees and in autumn and winter at 1.2 degrees.

The agency’s outlook for April to June also suggests above-average temperatures are likely, with a 60 percent chance in April and May and a 50 percent chance in June.

Experts attribute the unusually early heat to warming oceans. Maeng So-young, a climate columnist, said, “To understand why low-pressure systems are forming at this time of year, we need to look at the global system,” adding that warming seas generate rising air currents that influence weather patterns near Korea.

Global sea surface temperatures averaged around 30 degrees Celsius last month, the second-highest on record for March following 2024. “As oceans warm due to climate change, they can alter atmospheric circulation systems,” Maeng said. “Hot periods are arriving earlier, lasting longer and trending toward higher temperatures.”

This article from the Hankook Ilbo, the sister publication of The Korea Times, is translated by a generative AI system and edited by The Korea Times.