Sudden Storm And Fish Kill Rattle Jeju Island

Residents of Jeju Island woke on September 15, 2025, to a scene that few had ever witnessed: dead fish and shellfish littering the northern coast, particularly in the Yongduam and Doryeong areas of Jeju City. According to the Korea Meteorological Administration (KMA), this mysterious fish kill event, which lasted roughly an hour and a half, coincided with a sudden, torrential downpour that swept through the region during the late morning hours. The event was so striking that locals, making their way to lunch through the sheets of rain, found themselves soaked to the bone and bewildered by the spectacle unfolding along the shoreline.

Jeju City officials announced the fish kill at 11:30 AM, noting its rarity and the concentration of dead marine life in the northern and central parts of the island. The announcement, made public later that afternoon, quickly raised concerns about water quality and the potential impact of extreme weather on marine habitats. As reported by Jeju Maeil, residents expressed frustration and disbelief, with one remarking, "When it rains like this, even an umbrella is useless."

The heavy rain was not only a matter of inconvenience for those caught outdoors; it also triggered a wave of emergency calls to the local fire department. The Jeju Fire and Safety Headquarters responded to 24 incidents between 11 AM and 2 PM, most of them clustered in the northern areas. In Yongdam-dong, the coastal road cracked and a sinkhole appeared, prompting authorities to cordon off the area for safety. Other neighborhoods such as Gwangryeong-ri in Aewol-eup and Ora-dong experienced road flooding, while in Ido 2-dong, a manhole cover was dislodged by the deluge. Several semi-basement homes and building interiors in Yongdam-dong were also inundated, underscoring the intensity and suddenness of the storm.

Images provided by the Jeju Fire and Safety Headquarters showed the aftermath: battered coastal roads, emergency tape stretched across bike lanes, and the unmistakable signs of a community grappling with nature's unpredictability. As the afternoon wore on, the skies cleared and the immediate threat passed, but the sense of unease lingered. The fish kill, in particular, left many wondering about the connection between weather extremes and environmental health.

The KMA issued a weather forecast and warning update at 4:20 PM the same day, highlighting the broader pattern of unsettled weather across southern South Korea. Light rain had fallen in Jeju that morning, but the forecast warned of further precipitation for the island and neighboring regions over the next several days. From September 16, rain was expected to return to Jeju and much of the south, with predicted amounts ranging from 5 to 40 millimeters through the late afternoon, and 5 to 20 millimeters between the morning and late night of September 17. The KMA cautioned that the nature of these showers—localized and intense—could produce sharp differences in rainfall even within the same district. "Please refer to real-time weather radar images and the latest weather information," the KMA advised, urging residents to remain vigilant.

But rain wasn't the only concern. The forecast also called for continued high temperatures, with daytime highs in Jeju and other southern regions expected to reach up to 33 degrees Celsius. The combination of heat and humidity prompted heat advisories for coastal areas, and the risk of heat-related illnesses was flagged as a serious hazard, particularly for infants, the elderly, pregnant women, and those with chronic conditions. The KMA warned, "There is a high possibility of heat-related illnesses, so avoid outdoor activities and manage food carefully to prevent food poisoning."

For Jeju's fishermen and aquaculture operators, the warnings carried an extra layer of urgency. The KMA specifically noted that strong winds and heavy rainfall could impact water quality and fish habitats, potentially leading to additional fish kills like the one observed on September 15. The agency urged those in charge of livestock and aquaculture to lower animal density, provide cool and clean water frequently, and report any signs of mass mortality or disease to relevant authorities. "In areas under high-temperature advisories announced by the National Institute of Fisheries Science, please report any disease or mass death of farmed organisms to the authorities," the KMA stated.

Flooding, landslides, and coastal erosion were also on officials' radar. The forecast warned of possible flash floods in valleys and rivers, urging the public to avoid camping or approaching waterways during periods of heavy rain. Urban dwellers were reminded to steer clear of underground walkways, low-lying areas, and riverbank trails, as sudden inundation could lead to dangerous situations. The possibility of landslides, embankment collapses, and rockfalls was also highlighted, especially in areas where the soil had been saturated by repeated rainfall.

Looking ahead, the KMA predicted that the unsettled weather would persist through September 17, with further showers, thunderstorms, and gusty winds expected across Jeju and the southern mainland. The agency's warnings extended to maritime activities as well, as strong winds and high waves were forecast for the seas surrounding Jeju and the southern coast. Fishermen and boat operators were cautioned to monitor weather updates closely and avoid venturing out during periods of severe weather. "From the 17th, strong winds of 30 to 45 kilometers per hour and waves of 1.0 to 2.5 meters are expected in the distant seas off the west and east coasts," the KMA noted.

Amid all this, the specter of another fish kill loomed large. The KMA explicitly linked the risk of further marine mortality to the forecasted weather, noting that rapid changes in temperature, salinity, and oxygen levels—often triggered by heavy rain and storms—could stress or kill fish and shellfish in coastal and aquaculture environments. The events of September 15 served as a stark reminder of how quickly local ecosystems can be disrupted by extreme weather, and how closely human livelihoods are tied to the rhythms of nature.

For Jeju's residents, the past few days have been a lesson in resilience and adaptation. As emergency crews patched up roads, cleared debris, and responded to calls for help, many locals found themselves reflecting on the unpredictable interplay between climate, environment, and daily life. The KMA's repeated pleas for caution—"Pay special attention to the latest weather information and forecasts"—echoed across the island, a reminder that in an era of changing weather patterns, vigilance is more than just a virtue; it's a necessity.

As the skies over Jeju alternate between sun and storm, the community remains on alert, eyes turned both to the horizon and the sea, waiting to see what the next change in the weather will bring.