June 19, 2025
SEOUL – Following the beginning of this year’s monsoon season in Jeju Island on June 12, most of South Korea is also expected to enter the rainy season from Friday, according to the Korea Meteorological Administration.
Starting late Thursday afternoon, a stationary front is forecast to move northward from the southeast, as the North Pacific high-pressure system expands and pushes hot, humid air from southern China into the Korean Peninsula.
The Greater Seoul region, Gangwon Province and the North and South Chungcheong provinces, as well as North Jeolla Province, can expect to see rain from late Thursday afternoon due to a warm front forming ahead of a low-pressure system approaching from the west.
Nationwide rainfall will follow Friday and Saturday as the stationary front meets an expanding low-pressure system. The KMA anticipates Friday’s rainfall to begin the monsoon season in the central and southern parts of Korea, though further meteorological analysis is still needed for confirmation.
If the monsoon season begins nationwide Friday, according to the KMA’s weather predictions, it would be five days earlier than in previous years in the central region and three days earlier in the south.
Between 1991 and 2020, the average monsoon season starting dates were June 25 for the central region and June 23 for the southern region.
However, the KMA warned that rain clouds forming along the stationary front would likely be long but narrow. This means that the distribution of rainfall may be highly uneven, with some areas seeing thunderstorms while others seeing no more than drizzle.
Due to the development of multiple meso-scale low-pressure systems, the KMA stated that some areas could experience rainfall intense enough for heavy rain warnings to be issued. A heavy rain warning is issued in Korea when more than 90 millimeters of rain is expected to fall in three hours, or over 180 mm in 12 hours.
Korea frequently saw the development of these mesoscale low-pressure systems during its monsoon season in 2024, contributing to highly variable rainfall patterns and a sharp drop in forecast accuracy. A total of 16 instances of intense rainfall, exceeding 100 mm per hour, were recorded.
From June 22-24, the KMA added that concentrated rainfall will fall again on Jeju Island, as the stationary front is expected to remain over the island and the southern coast. The front may then move again northward on June 25, bringing more rain to the rest of the country — though this is subject to change.
As the monsoon season sets in, average nationwide temperatures are expected to drop from Friday. In Seoul, high temperatures are expected to be 1 to 2 degrees Celsius lower or similar to average temperatures from previous years from Friday.
However, humidity levels are still anticipated to rise, as large volumes of moisture remain stagnant in the atmosphere, meaning the weather will feel hotter, despite the lower temperatures.