Erratic April weather has Koreans in seasonal disarray

April weather in Korea has been erratic, with significant temperature swings causing colds among residents. However, stabilization is expected, with milder temperatures forecast for the end of the month.

A citizen visiting N Seoul Tower, a landmark Seoul building with a transmission antenna sitting atop Namsan, is seen wiping away sweat as Seoul is seeing warm weather on April 17. [YONHAP]

Oh, a 30-something office worker in Seoul, said they've been under the weather throughout April due to the erratic swings in temperature.

“Being frozen and heated up again and again, I feel like dried fish," said Oh. “It’s been warm like spring one day and cold the next, and the temperature gap from day to night is huge. A lot of people around me are catching colds.”

On Friday morning, temperatures in parts of Seoul dropped to 2.6 degrees Celsius (36.7 degrees Fahrenheit) in Eunpyeong District, northern Seoul. Office workers bundled in padded jackets were spotted around Gwanghwamun, central Seoul.

Temperatures in mountainous inland regions such as Muju, North Jeolla and Hoengseong, Gangwon, dipped below freezing, while northern Gyeonggi hovered near zero.

The morning chill was caused by a mass of cold air around zero degrees Celsius at an altitude of 1.5 kilometers (0.39 miles) blanketing central Korea. The Korea Meteorological Administration (KMA) said that "the clear skies overnight intensified radiative cooling, causing some inland areas to drop near freezing."

So far this month, the nationwide average temperature has been 12.7 degrees Celsius, similar to the annual average of 12.1 degrees Celsius for April. However, compared to last year — which experienced unseasonal warmth beginning in spring — cold spells have been more frequent.

In mid-April, Seoul saw dramatic temperature shifts, even snow. On April 11, the daytime high reached 24.2 degrees Celsius, but by April 14 it plunged to 6 degrees Celsius, only to bounce back to 24.7 degrees Celsius on April 17. The 18-degree Celsius swing in just three days exemplifies the month's volatility.

A visitor to N Seoul Tower, a landmark Seoul building with a transmission antenna sitting atop Namsan, is seen wiping away sweat as Seoul experiences fluctuating hot-cold weather conditions on April 17. [YONHAP]

Meteorologists attributed April’s pronounced fluctuations to strong low-pressure systems and weakened Arctic jet streams.

“When low pressure passes over Korea, northwesterly winds often follow,” Chang Eun-chul, an atmospheric science professor at Kongju National University. “This year, those systems were not only stronger but moved more slowly, resulting in longer cold spells.”

Low-pressure systems also brought rain nearly every weekend. Temperatures dropped after the rain, while warm air from the northwestern Pacific — which remained mild — quickly raised temperatures when cold air wasn’t present.

Ban Ki-seong, head of K Weather, noted that a weakened Arctic jet stream is influencing East Asian weather. The jet stream, which normally circulates cold air around the Arctic, allows polar air to spill into the mid-latitudes when it weakens.

A cut-off low that broke away from the jet stream triggered extreme weather in mid-April across Korea, China, and Japan, including strong winds, hail, and snow. Containing polar air as cold as minus 30 degrees Celsius, the system brought unusually intense conditions.

For now, high pressure will stabilize conditions over the Korean Peninsula, likely reducing dramatic temperature swings. The KMA forecasts that through the end of April, temperatures will remain near or slightly below seasonal norms.

Morning lows across most of the country are expected to stay below 10 degrees Celsius, especially in inland regions, while daytime highs will reach around 20 degrees Celsius — ushering in a mild and pleasant spring.

Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff. BY JEONG EUN-HYE [kim.minyoung5@joongang.co.kr]