South Korea faces nationwide rain, unhealthy air in Seoul region; landslide threat.
A low-pressure system moving eastward from the southwestern seas is expected to bring rain nationwide on Wednesday, with the heaviest rainfall in the central and western parts of the country. The rain will begin in the early hours and spread across most areas through the day, with Jeju Island likely experiencing the strongest shower activity.
Air quality is a concern tied to this weather pattern. Authorities said that on the 18th, air pollution levels are expected to be "unhealthy" in the Seoul metropolitan area, western Gangwon, and parts of Chungcheong. Other regions are forecast to be mostly normal, though some northern and southern areas may still see unhealthy levels through the morning.
Temperatures on the 18th are projected to range from a morning low of 1 to 10 degrees Celsius and a daytime high of 9 to 14 degrees. They will be similar to, or slightly above, Korea’s seasonal norms, which typically run from -2 to 6 degrees at night and 11 to 15 during the day.
Rainfall amounts vary by region. Seoul, Incheon, and Gyeonggi Province are expected to see less than 5 mm. Daejeon, Sejong, and parts of Chungcheong may record 5–10 mm, while Gwangju and Jeollabuk-Jeollanam provinces could see 5–20 mm. The southern Sae and Jeju regions are forecast to receive 10–50 mm, with some mountainous areas exceeding 70 mm.
The weather poses practical hazards. Reduced visibility and slippery roads are likely where rain is heaviest. The combination of thawing ground and falling rain raises the risk of landslides, mudslides, and the potential collapse of retaining walls in vulnerable areas.
Winds on Jeju Island could reach around 55 km/h, with strong gusts capable of affecting coastal facilities and outdoor activity. Thunderstorms with lightning are possible over southern coastal waters.
Why this matters for the United States. Heavy rain and deteriorating air quality in Korea can disrupt manufacturing and logistics at a major East Asian hub for semiconductors, autos, and consumer electronics, potentially affecting supply chains that stretch to U.S. manufacturers and retailers. Atmospheric conditions tied to northwest-origin dust and East Asian weather patterns also intersect with regional health and environmental policy efforts that involve the United States and South Korea, including air-quality management and climate cooperation. For travelers and exporters, understanding the timing of rain, wind, and visibility helps anticipate disruption to flights, port operations, and distribution networks.
Context for non-Korean readers. The Korea Meteorological Administration issues nationwide forecasts and warnings. Jeju is Korea’s largest island off the southern coast, while the West Sea refers to the Yellow Sea between Korea and China. The regions named—Seoul metropolitan area, Gangwon, Chungcheong, Jeolla, and Gyeongsang—are standard administrative divisions used in weather reporting.