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Korea's 'missing monsoon': Less rain than usual sparks debate over weather term

Published: 03 Jul. 2025, 07:00 Updated: 08 Jul. 2025, 15:41

A child cools off from the heat with water at a park in Buk District in Gwangju on June 23. [NEWS1]

At the Korean Meteorological Administration's (KMA) academic conference in May, a heated debate broke out over the definition of a monsoon. A survey showed that most meteorologists agreed the traditional concept of the monsoon has changed. But opinions were split on whether to adopt a new term like "rainy season."

"The monsoon is changing into an unpredictable pattern, and even this summer doesn't reflect a typical monsoon,” Son Seok-woo, head of the KMA's monsoon special weather center and professor of the Department of Earth and Environmental Sciences at Seoul National University, told the JoongAng Ilbo on Wednesday.

"It's time we redefine the monsoon, even if it means rewriting the textbooks."

This summer, the monsoon has not lived up to its name. It began earlier than usual, starting June 12 in Jeju Island and June 19 in central and southern regions, according to the KMA. But after an initial downpour exceeding 60 millimeters (2.36 inches) per hour, monsoon rains have largely vanished.

In Seoul, more than 50 millimeters of rain fell on June 19 and 20, but the total precipitation from June 21 to July 1 was a mere 13.3 millimeters. The term “missing monsoon” is gaining traction.

This anomaly is due to the North Pacific high-pressure system expanding faster than expected and pushing the monsoon front northward over the Korean Peninsula. As a result, rainfall has subsided, replaced by sweltering heat and a cycle of tropical nights.

Citizens walk by a downtown area in Daegu with iced coffee and portable electric fans as heat advisories were issued in the region on June 28. [YONHAP]

Cooling fog sprays mist in a jjokbang, or subdivided housing area, in Jongno District, central Seoul, on June 11, as early summer heat sets in. [JOONGANG ILBO]

Textbook monsoon outdated

Textbooks define the Korean monsoon as a prolonged rainfall caused by the collision of the North Pacific air mass from the south and the Sea of Okhotsk air mass from the north over the Korean Peninsula.

But many scholars say this textbook model is outdated. With frequent localized heavy rains — resembling tropical downpours — and the increasing use of the term "multiphase monsoon," it's becoming harder to pinpoint a clear monsoon period. Some are calling for a redefining of the phenomenon as a "Korean-style rainy season."

"The idea that the monsoon is caused by the collision of the North Pacific and Okhotsk air masses is as implausible as Mike Tyson fighting a kindergartner — the theory no longer holds up," said Kim Hae-dong, a professor of environmental engineering at Keimyung University.

He explained that climate change is intensifying surface heating, leading to strong, localized downpours unrelated to the monsoon front.

A heat haze caused by ground temperature rose above Yeouidaero in Yeongdeungpo District, western Seoul, on June 15, as daytime temperatures in Seoul surpassed 30 degrees Celsius. [YONHAP]

Dry monsoon ushers in heat

The dry monsoon has brought unprecedented heat. Wednesday’s temperature in Miryang, South Gyeongsang, soared to 38.3 degrees Celsius (100.9 degrees Fahrenheit) — the highest ever recorded in early July since records began in 1973. It beat the previous record of 36.7 degrees Celsius set on July 10, 1994.

In Gangneung, Gangwon, the first super tropical night of the year began Tuesday. From 6:01 p.m. Tuesday to 9 a.m. Wednesday, the lowest temperature in Gangneung was 30.3 degrees Celsius.

A tropical night is defined as one where temperatures remain above 25 degrees Celsius overnight. A super tropical night occurs when temperatures exceed 30 degrees Celsius. Super tropical nights this early in July are highly unusual.

Heat-related illnesses are also rising. A total of 508 people suffered from heat-related conditions from May 20 to July 1 — a 30.3 percent increase from the same period last year, according to the Korea Disease Control and Prevention Agency (KDCA). Including patients from the early surveillance period between May 15 and 19, the total number reached 524. Three deaths, which are likely heat related, have been reported so far.

Beachgoers crowd Gyeongpo Beach in Gangneung, Gangwon, on June 29 to beat the heat. [YONHAP]

Heat haze rises over Dalgubeol Boulevard in Suseong District, Daegu, on June 23 as the mercury climbs past 30 degrees Celsius during a break in the monsoon rains. [NEWS1]

Could the 2018 heat wave repeat?

The outlook remains uncertain. There's no sign of monsoon rain through the upcoming weekend, according to the KMA. While showers may occur in central regions due to atmospheric instability, they are unlikely to offset the heat.

If the monsoon ends this way, there are concerns of a repeat of the extreme heat in 2018, when the monsoon ended early on July 11 in central Korea, triggering a record-breaking heat wave. That summer, the country saw 31 days of high temperatures nationwide — a record still unbroken.

However, the KMA says it's too early to officially declare the end of the monsoon.

"The monsoon front is currently located 200 to 300 kilometers [124 to 186 miles] north of the Seoul metropolitan area, in North Korea," said Woo Jin-kyu, a spokesperson for the KMA. "Although a high-pressure system is dominating the country now, changes in pressure systems — such as disturbances over the Philippine Sea — could bring the monsoon front back, so we can't conclude it's over yet."

Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff.
BY CHON KWON-PIL [[email protected]]