Jeju monsoon rain is expected to begin on Thursday, marking an unusually early start to the season. The Korea Meteorological Administration confirmed the forecast on Wednesday as Typhoon Utip continues moving north. Moreover, rainfall will likely expand to southern mainland regions by Friday morning. The KMA attributes this pattern to a stationary front positioned south of Jeju. Notably, this front formed due to typhoon activity along the Philippine coast.
Furthermore, the weather agency expects the North Pacific high-pressure system to push the stationary front northward. This action will likely trigger Jeju monsoon rain ahead of the usual schedule. On average, Jeju sees monsoon conditions begin around June 19. Therefore, if the pattern holds, this year’s arrival could be a full week early. Consequently, it would become one of the three earliest monsoon starts on record.
By Thursday, rain will sweep through Jeju and move eastward toward nearby provinces. Specifically, South Jeolla and South Gyeongsang could see up to 40 millimeters of rain. In contrast, Jeju itself may face downpours reaching 60 millimeters throughout the day. As the stationary front advances, North Jeolla and southern parts of North Gyeongsang may get 5 to 20 millimeters. Thus, the weather will remain unstable across southern Korea.
In the afternoon, North Chungcheong and northern parts of North Gyeongsang will likely experience scattered showers. Rainfall in these regions will range between 5 and 10 millimeters. Meanwhile, hot and humid air from the east of the Philippines will move inland. This moisture, combined with the high-pressure system, strengthens the likelihood of extended rainfall. Overall, the front’s movement remains steady and widespread.
Additionally, Jeju monsoon rain may reach the greater Seoul area and Gangwon Province by Friday. Rain is expected to clear up later that evening in most areas. However, meteorologists warn that only Jeju’s rain qualifies as official monsoon rainfall. In fact, the rest of the country will likely wait longer for formal monsoon conditions. After all, the source of the rain must be the stationary front to meet that definition.
Looking ahead, heavy rain is expected again from Sunday to Monday. A cold air mass will descend from the north during that time. Then, it will collide with the humid southern airflow over the peninsula. This clash could result in intense nationwide showers for two days. Ultimately, Jeju monsoon rain, therefore, signals the season’s accelerating shift.
