Intense nighttime downpours are flooding South Korean cities and damaging infrastructure as climate change alters regional weather patterns [1].
These "water-bomb" storms pose a critical risk to urban populations, particularly those living in semi-basement homes where rapid flooding can become lethal. The shift toward localized, high-intensity nighttime rain complicates emergency responses and infrastructure resilience.
In August 2022, the southwest district of Seoul experienced rainfall intensity that exceeded 140 mm per hour [1]. The deluge turned city streets into rivers and flooded numerous semi-basement residences [1].
Similar extremes occurred in July 2023 in Seosan city, located in South Chungcheong Province [1]. That event was described as a once-in-200-years water-bomb [1]. The storm produced more than 2,500 lightning strikes and damaged equipment belonging to the Korean Meteorological Administration [1].
Scientists said these events are attributed to rising carbon emissions, which increase the amount of water vapor in the atmosphere [1]. Specifically, a 1 °C rise in temperature increases atmospheric water vapor by seven percent [1]. This moisture creates unstable air that forms intense, localized clouds via low-level jet streams during the night [1].
Regional warming is accelerating this trend. Since 2010, the rise in sea-surface temperatures in the West Sea and South Sea has been more than twice the previous average increase of 0.14 °C [1].
“Rainfall intensity in Seoul exceeded 140 mm per hour”
The increasing frequency of these 'water-bomb' events suggests that South Korea's historical rainfall data may no longer be a reliable guide for urban planning. As sea-surface temperatures in the West and South Seas rise faster than global averages, the atmospheric capacity for moisture increases, making extreme, short-duration nighttime floods a systemic rather than episodic threat to the peninsula's infrastructure.
