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Roads and major intersections across Okpo-dong, Geoje, South Gyeongsang Province, are completely submerged in muddy water on the 17th. / Yonhap

South Korea's southeastern coast — including Geoje and Tongyeong in South Gyeongsang Province — saw the heaviest rainfall on record over the three-day Liberation Day holiday. In just three days, these areas received rain equivalent to an entire summer monsoon season, causing casualties and property damage.

According to the Korea Meteorological Administration, as of 3:28 p.m. on the 17th, Geoje recorded 625.2mm of rain within a single day — the highest daily rainfall since modern weather observation began there in 1972. Nationwide, this ranks third all-time, behind readings recorded in Gangneung and Daegwallyeong during Typhoon Rusa's landfall on the Korean Peninsula in 2002. Tongyeong also recorded its highest daily rainfall on record, at 447.2mm as of the same time.

Hourly rainfall — a key factor directly tied to flood damage — also set new records. In Geoje, 124.5mm fell within a single hour starting at 1:32 a.m. that day, far surpassing the previous record of 96.5mm set on July 5, 2001. Tongyeong likewise set a new record with 97.4mm falling in one hour starting at 5:11 a.m.

Rainfall over the three-day Liberation Day holiday alone matched the average total rainfall for an entire summer. Geoje and Tongyeong received 898.4mm and 743.4mm, respectively, from the 15th to the 17th, compared with their average summer rainfall (1991-2020 average) of 935.1mm and 728.8mm.

This "monster downpour" was caused by a low-pressure system that formed as Typhoon No. 13, Dolphin — which originated near Guam — weakened near Shanghai, China, and approached Korea from the southwest. Hot, humid winds flowed in alongside the low-pressure system, and rainfall concentrated heavily along the South Coast, an area strongly affected by local terrain.

As a result, landslides, flooding, and facility damage occurred in succession, mainly along South Gyeongsang Province's coastal areas, leaving one person dead and prompting 136 rescues. About 160 residents in areas including Geoje evacuated, and power outages also occurred in some homes.

                                                                                                           Kim Hong-chan