Monsoon season to start early on Jeju Island from Thursday

Jeju Island is expected to witness the start of this year’s monsoon season on Thursday, with the rain expanding northward until Saturday, according to the Korea Meteorological Administration, Wednesday.

Starting early Thursday, rain is expected on Jeju Island due to a stationary front situated south of the region. According to the KMA, the front formed under the influence of Typhoon Utip, the first typhoon of the summer, as it moved northward along the western coast of the Philippines toward southern parts of China.

The state weather agency expects the North Pacific high-pressure system to expand westward, pushing the stationary front northward to trigger Jeju Island’s first monsoonal rains of the season.

This year’s monsoon season is projected to have an earlier start, with Jeju Island normally seeing monsoon rain around June 19 on average. If weather conditions persist, this year’s monsoonal rains will come a week earlier than usual and would mark the third-earliest monsoon season on record, trailing only 2020 and 2011's June 10 and matching 1998's June 12.

On Thursday, the stationary front is expected to move eastward, while hot and humid air from the east of the Philippines will flow into the Korean Peninsula along the edge of the North Pacific high-pressure system. This will bring heavy rains of up to 60 millimeters to Jeju Island, and up to 40 mm of rain to South Jeolla Province and South Gyeongsang Province. Rain clouds will also expand toward North Jeolla Province and southern parts of North Gyeongsang Province by late morning, bringing close to 5 to 20 mm of rain.

By the afternoon, North Chungcheong Province as well as northern parts of North Gyeongsang Province can also expect to see rain, ranging between 5 and 10 mm.

The KMA added that rain clouds will spread to most regions nationwide, including the Greater Seoul region and Gangwon Province, by Friday, before clearing up later that night.

Despite widespread rainfall, KMA meteorologist Gong Sang-min added that this week’s rain is unlikely to mark the official start of monsoon season for other parts of Korea aside from Jeju Island. This is because rain must be triggered by a stationary front to be considered monsoonal rain, not simply from other systems.

Though subject to change, heavy rainfall is also expected to fall nationwide from Sunday to Monday, due to a clash between humid air flowing in from the south and a cold air mass moving down from the north.