Starting from the night of Thursday, the 19th, this year's 'monsoon' will begin in the central and southern inland areas. In particular, heavy rain is expected to pour overnight on Friday, the 20th. After a brief lull over the weekend, rain will spread across the southern region and Jeju early next week and then expand nationwide by the end of next week.
Kong Sang-min, a forecast analyst at the Korea Meteorological Administration, noted during the regular forecast briefing on the 19th, "Some areas in the western coastal region will see sporadic rain starting tonight, and this rain will signal the start of the monsoon season in the central and southern regions this summer."
This year's inland monsoon in the central and southern regions is occurring 4 to 6 days earlier than usual. Previously, the monsoon was declared early in Jeju on the 12th, which was also 7 days earlier than normal.
Rain is forecast to begin in the late afternoon of the 19th, starting from the western coast and the northwestern part of the metropolitan area. The Gyeongsang and Jeolla regions are expected to either experience no rain or sporadic rain.
From the evening of Friday, the 20th, until the morning of Saturday, the 21st, strong rain is expected as a stationary front approaches. There is a possibility of a medium-sized low pressure developing along this front, which will bring intense rainfall of 30 to 50 mm per hour, particularly in the central region and North Jeolla area. Rain falling at over 30 mm per hour will be so strong that visibility will be severely reduced even with windshield wipers operating at maximum speed.
On Saturday, the 21st, due to the influence of cold air descending from the north, the stationary front will retreat southward, bringing rain primarily to Jeju and the southern regions. Between the 19th and the 21st, heavy rainfall of over 150 mm is expected in northern Gyeonggi, western Gangwon, southern Chungcheong, and North Jeolla.
The Korea Meteorological Administration especially urged caution between the night of the 20th and the morning of the 21st. Analyst Kong said, "River levels in northern metropolitan areas and near the North Korean border may rise sharply, posing a risk of fast currents, so campers should avoid approaching these areas," adding, "Attention should also be paid to flooding when passing through tunnels and underpasses."
Rain falling primarily in the central region will stop by the weekend. During this time, daytime temperatures will rise significantly in the metropolitan area, resulting in hot weather.
In the early part of next week, from the 22nd to the 24th, the stationary front will move southward, bringing rain to the southern coast and near Jeju. The central region will experience occasionally cloudy weather. From the 25th to the 27th, this front will once again move northward, resulting in rain across the country. Next week is expected to have temperatures around the normal level, but the influx of humid air will likely cause a higher perceived temperature.