South Korea's southern coast is experiencing a rise in extreme heavy rain events exceeding 100 mm per hour [1].
These patterns signal a shift in seasonal weather risks, as extreme precipitation is now occurring more frequently during late summer and early autumn. This trend threatens infrastructure and public safety in coastal regions that may not be prepared for such intensity outside the traditional monsoon window.
Geoje city, located on the southern coast of Gyeongsangnam-do, faced record-breaking rainfall on Aug. 17, 2024 [1]. This event is part of a broader trend where "extreme heavy rain" is becoming more common through August and September, a YTN News anchor said [1].
Data shows that these high-intensity events are recurring. In 2023, there were 15 total events exceeding the 100 mm per hour threshold, with 11 of those occurring in August and September [1]. During the same period in 2024, seven such events were recorded [1].
Beyond Geoje, other regions have been affected. On Sept. 21, 2024, five different southern locations experienced similar extreme rainfall [1].
Several factors contribute to these volatile weather patterns. High temperatures and elevated sea-surface temperatures have increased atmospheric moisture [1]. These conditions, combined with seasonal shifts in atmospheric pressure and broader climate-change trends, increase the likelihood of sudden, extreme rain events [1].
Journalist Kim Min-kyung said that record rainfall hit Geoje on the 17th [1]. She said that seven similar events appeared during the same period in 2024 [1].
“Extreme heavy rain exceeding 100 mm per hour has become more frequent in August and September.”
The shift of extreme rainfall into August and September suggests that South Korea's traditional rainy season is expanding or evolving. The combination of rising sea-surface temperatures and atmospheric moisture creates a feedback loop that intensifies precipitation. This requires a reassessment of urban drainage systems and emergency response timelines to account for high-intensity flooding occurring later in the year than historically expected.
