An extraordinary late-summer rainfall event has battered southern and central South Korea, dumping nearly 580 mm (22.8 in) of rain in parts of South Jeolla and triggering flash floods, landslides and hundreds of emergency responses.
The heaviest rainfall initially focused on the southwest before spreading north and east into North Jeolla and the Chungcheong region on Monday, August 31.
Yeonggwang in South Jeolla emerged as one of the hardest-hit areas. Accumulated rainfall since August 28 reached 579.5 mm (22.8 in), while Nakwol Island recorded an exceptional 103.5 mm (4.1 in) in just one hour early Monday.
More than 100 mm falls in one hour
Nakwol Island recorded around 344 mm (13.5 in) during Monday alone, highlighting the extraordinary intensity of the latest phase of the storm.
Other parts of western South Korea also received exceptional rainfall. Gunsan accumulated more than 340 mm (13.4 in) during the broader rainfall episode, while Seocheon and Buyeo in South Chungcheong approached or exceeded 260 mm (10.2 in).
🚨 Severe flooding was caused by heavy rainfall in Gwangju & South Chungcheong, South Korea.
— Weather Monitor (@WeatherMonitors) July 17, 2025
Over 400 mm of rain, with more expected tonight.
⚠️ 2 dead, 1,000+ evacuated
-Landslide alert at highest level
-403 schools closed, 166 damaged
-87 roads & 38 buildings… pic.twitter.com/9HOIT8cSih
The rain caused rivers and streams to rise rapidly. Residents near the Jujin Stream in Gochang were ordered to evacuate Monday morning as water levels increased, while Gochang experienced rainfall rates of around 60 mm (2.4 in) per hour.
Flooding affected homes, roads and other buildings across the southwest, while landslides and rockfalls created additional hazards in hillier areas.
Hundreds of emergency responses
South Korea’s fire and emergency services had carried out 474 safety operations by Monday afternoon, responding to flooded homes, blocked roads, drainage problems, landslides and debris.
At least 42 people from 29 households were temporarily evacuated across six provinces and cities.
Transport was also disrupted, with flights and ferry services suspended and thousands of sections of riverbanks, riverside parking areas and other potentially dangerous locations closed.
The human impact became more serious through Monday. A 73-year-old man was reported missing in Jeongeup after leaving to work near a rice field. Authorities were also searching for a 67-year-old man who disappeared while working at a greenhouse in Gochang.
Why has the rainfall been so extreme?
The event is being driven by an exceptionally moisture-rich late-summer air mass interacting with a slow-moving frontal and convergence zone across the Korean Peninsula.
Warm, humid air moving north across the Yellow Sea has provided thunderstorms with a deep supply of atmospheric moisture.
Instead of moving quickly through the region, thunderstorms repeatedly developed along similar corridors. This process, known as training convection, allows intense cells to cross the same locations one after another, rapidly building extreme rainfall totals.
The unusually warm Yellow Sea may also be increasing the moisture available to the storms. Sea surface temperatures have been reported near 29°C (84°F), around 4°C (7°F) above average in some areas.
Combined with strong atmospheric instability, this has created highly efficient rainfall-producing thunderstorms. The 103.5 mm recorded on Nakwol Island in only one hour demonstrates how quickly flooding can develop under such conditions.
Flood threat shifts north
The focus of the heaviest rain began migrating toward central South Korea later Monday, with parts of the Chungcheong region reporting flooded roads, fallen trees and additional emergency incidents.
Authorities activated Level 1 of the Central Disaster and Safety Countermeasures Headquarters and raised the national heavy-rain crisis alert from “Interest” to “Caution.”
Although the most extreme rainfall has eased across some southwestern areas, soils remain heavily saturated and rivers elevated.
Additional thunderstorms could therefore trigger new flash flooding, landslides and rapid river rises even where rainfall is less extreme.
With the frontal zone continuing to shift across the peninsula, the flood and landslide threat remains active as South Korea enters September.
