Starting on the 26th, rain will fall nationwide, with very heavy rain forecast to pour down mainly along the South Coast and on Jeju Island. In Jeju's highlands, torrential downpours of more than 250 mm are expected.
According to the Korea Meteorological Administration, rain will fall over most regions nationwide from this day through the morning of the 27th, and in South Jeolla, the Gyeongsang region, and Jeju Island, rain will continue through late afternoon on the 27th.
Expected rainfall is 50–100 mm on Jeju Island (excluding the north), with more than 150 mm in many mid-mountain areas and more than 250 mm in the highlands. South Jeolla and South Gyeongsang will see 30–80 mm, with some places along the South Coast and near Jirisan Mountain receiving more than 100 mm. The Seoul metropolitan area, Gangwon, Chungcheong, North Jeolla, Daegu, and North Gyeongsang are forecast to get 10–60 mm.
In particular, very heavy rain of around 30–50 mm per hour is expected to concentrate mainly on Jeju Island and the South Coast. In Jeju's highlands, there is a possibility of torrential downpours of around 50 mm per hour. In areas seeing rain, some places will also get thunder and lightning with gusts.
The Korea Meteorological Administration urged people to take special care for safety in preparation for possible damage from river flooding, low-lying area inundation, landslides, and falling rocks. It said people should refrain from approaching valleys or rivers, as water levels can rise rapidly due to heavy rain in a short time.
High winds are also forecast. On Jeju Island and along the South Jeolla coast, very strong winds with instantaneous speeds of more than 20 meters per second (more than 25 meters per second in the highlands) will blow through the morning of the 27th, and most other regions nationwide are expected to see strong winds with instantaneous speeds of around 15 meters per second.
At sea, waves will be very high at up to 3.5 meters mainly in the far seas off Jeju Island and the South Coast, and gusts and thunder and lightning may accompany them, requiring caution for vessels sailing or fishing.
On the 28th, another round of about 5 mm of rain will fall mainly in the central region and the Jeolla region, then from the 29th the weather will be mostly cloudy or clear.