South Korea Braces for Nationwide Rain, Mountain Snow; Air Quality Varies

Rain is expected to sweep across South Korea on Wednesday, with showers reaching most parts of the country by the afternoon. The southern regions are likely to see rainfall wash away much of the fine dust, bringing air quality back to a moderate level, while the central regions are expected to retain higher levels of fine dust.

Rain is forecast to begin in the dawn hours in Gyeonggi southern areas, Chungcheong, Honam, southwestern Gyeongsang, and Jeju, spreading nationwide by the afternoon. Some parts of eastern Gyeonggi Province and inland Gangwon Province, including mountainous areas, may see snow instead of rain. Rain could continue along the southern coast and Jeju into the night.

Forecast rainfall totals vary by region: Jeju is projected to receive 10 to 50 millimeters, with the mountains possibly exceeding 70 millimeters. Southern Jeollanam-do, Busan, and the southern coast of Gyeongsang are expected to accumulate 10 to 30 millimeters, while other areas such as Gwangju, northern Jeollanam-do, Jeonbuk, Ulsan, and inland Gyeongsang may see 5 to 20 millimeters. The Seoul metropolitan area, Gangwon Province, Chungcheong, Daegu, and North Gyeongsang are expected to receive 5 to 10 millimeters, with Ulleungdo and Dokdo likely under 5 millimeters. Snow is also possible at elevations above 1,000 meters in Gangwon.

Jeju could experience strong winds from the afternoon of the 18th into the morning of the 19th, with gusts around 55 kilometers per hour, and up to about 70 kilometers per hour on high ground. Residents and travelers to Jeju should prepare for gusty winds and possible blustery conditions.

Air quality forecasts from the National Institute of Environmental Research indicate improving conditions in the southern regions due to rain, with air quality returning to a moderate level. In contrast, central regions could see dust persistent or worsen due to domestic emissions, keeping the overall air quality at or above the “bad” level. The forecast also notes very poor or worse conditions in parts of the capital region and western Gangwon on the morning of the 18th, with other areas such as Sejong, Chungbuk, Gwangju, Jeonbuk, Daegu, and Daegu’s northern areas remaining in the bad range through the morning.

Temperatures are expected to range from morning lows of 1 to 10 degrees Celsius to daytime highs of 9 to 14 degrees, roughly in line with or slightly below seasonal norms. In major cities, the forecast calls for Seoul to range from about 6/11 degrees, Incheon 5/9, Gwangju 7/13, Daegu 7/13, Ulsan 7/11, and Busan 10/14.

Maritime conditions around the southern coast and Jeju’s adjacent seas are expected to be rough, with winds of 25 to 60 kilometers per hour and waves reaching 1.0 to 3.5 meters. Authorities may issue warnings or advisories, so seaborne traffic and coastal activities should monitor updates.

For U.S. readers, the forecast matters for several reasons. South Korea is a major hub in global supply chains, including electronics and automotive components, and heavy rain and wind can disrupt port operations and logistics, potentially affecting shipments to and from major gateways such as Busan and Incheon. The expected deterioration in air quality in central regions may influence cross-border health advisories and travel planning, particularly for visitors and workers with respiratory sensitivities. Finally, Jeju’s weather impacts tourism and regional energy demand, which can have ancillary effects on markets and travel costs in Asia. Officials expect updates as the system evolves, so staying aligned with local weather advisories is advisable.