The summer monsoon began on Jeju Island on June 30, 2024, marking the third-latest onset since records began in 1973 [1].
This delayed arrival of the rainy season is significant because it disrupts typical agricultural and weather patterns, contributing to extreme heat in the Seoul metropolitan area and other inland regions while the stationary front remains south.
The onset of the monsoon occurred 11 days later than the climatological average [2]. It also arrived 18 days later than the previous year [1]. A YTN anchor said the weather event is a "delayed monsoon," noting that the rains are expected to expand to the southern coast by July 1, 2024 [1].
Meteorologists attribute the delay to the movement of a stationary front. This front has created a thick, band-like cloud formation stretching from southern China, through Jeju Island, and into Japan, according to YTN reporter Jung Hye-yoon [1]. The northward progression of this front is what eventually triggered the rains in Jeju, though it has kept the inland monsoon delayed.
While Jeju begins its rainy season, the central region of South Korea continues to experience "steamer-like" heat. The absence of the monsoon rains in the Seoul area has prevented the usual cooling effect that accompanies the summer rains, leaving the metropolitan region trapped in high temperatures.
Weather officials expect the rain to continue spreading northward from the southern coast. The transition from extreme heat to heavy rainfall often creates volatile weather conditions for the mainland as the stationary front finally arrives.
“The summer monsoon began on Jeju Island on June 30, 2024, marking the third-latest onset since records began in 1973.”
The delayed onset of the monsoon in Jeju Island reflects a broader disruption in regional weather patterns. When the stationary front lingers south of the mainland, it prevents the precipitation that typically moderates summer temperatures, thereby intensifying heat waves in urban centers like Seoul. This lag between the expected and actual start of the rainy season can lead to increased agricultural stress and heightened public health risks associated with prolonged extreme heat before the eventual arrival of heavy rains.
