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Heavy rain warnings anticipated as monsoon draws nearer

Published: 17 Jun. 2025, 19:03

A pedestrian uses a bag to avoid the rain while walking near near Gwanghwamun Square on June 16. [YONHAP]

The summer monsoon season is expected to begin across the country around Friday, bringing potentially torrential rains, the Korea Meteorological Administration (KMA) said Tuesday.

Heavy rainfall warnings are likely to be issued in some regions due to intense and prolonged downpours, prompting authorities to warn of possible weather-related damage.

As the North Pacific high-pressure system expands, hot and humid air from southern China will flow into the Korean Peninsula, according to the KMA. By Thursday and Friday, both central and southern regions are expected to come under the influence of a stationary front.

In central areas and North Jeolla, rain is forecast to begin late Thursday into the night due to a warm front forming ahead of a low-pressure system approaching from the west. The monsoon front is then expected to bring rain nationwide on Friday and Saturday.

Jeju Island already entered the monsoon season on June 12, about a week earlier than average. If the rainy season begins nationwide on Friday, it would be five days earlier than usual in the central region and three days earlier in the south.

Visitors walk around a garden in Andeok-myeon, Seogwipo, on Jeju Island with umbrellas on June 12, with Korea's monsoon season to start with rain on the island the same day. [YONHAP]

The average monsoon starting dates between 1991 and 2020 are June 25 for the central region and June 23 for the south. The KMA noted that the official start date of the monsoon may change after further analysis.

In particular, some areas could experience rainfall intense enough to trigger heavy rain warnings, which are issued when more than 90 millimeters (3.54 inches) of rain falls in three hours or over 180 millimeters in 12 hours.

Such extreme rainfall early in the season is due to the development of multiple meso-scale low-pressure systems along the stationary front.

These systems supply additional moisture and destabilize the atmosphere, potentially leading to heavy downpours accompanied by thunder and lightning. With an average duration of around 10 hours, these systems are difficult to predict.

Pedestrians with umbrellas cross Sejong-daero, a street in Jongno District, central Seoul, on June 16 as rain pelts the country. [YONHAP]

Lee Chang-jae, a forecast analyst at the KMA, warned that “narrow, linear rain bands could cause stark differences in rainfall between adjacent areas, requiring preemptive caution.”

From June 22 to 24, the monsoon front is expected to remain over Jeju and the southern coast, concentrating rainfall in those regions. The front may move north again around June 25, potentially bringing more rain to the rest of the country.

As the monsoon fully sets in, the intense early summer heat is expected to ease. Morning temperatures are likely to remain above average for the time being, while daytime highs are expected to be close to seasonal norms.

However, as large volumes of moisture enter the atmosphere, humidity levels will rise, leading to high apparent temperatures. In areas where the rain briefly lets up, sweltering conditions are likely to persist.

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