South Korea is experiencing late-summer daytime temperatures hovering around 30 degrees Celsius alongside dense morning fog, according to a weather forecast issued on Sept. 21, 2026, by Yonhap NewsTV weather forecaster Hwang Seo-hee.
The weather system brings clear skies nationwide heading into the Chuseok holiday period, though travelers should prepare for stark temperature swings and localized coastal hazards. Morning temperatures in Seoul start at 18 degrees Celsius, while daytime highs in Seoul and Cheongju reach 29 degrees Celsius. Southern regions see even higher readings, with Gwangju hitting 31 degrees Celsius, Jeonju reaching 30 degrees Celsius, and Daegu registering 28 degrees Celsius—temperatures sitting 3 to 5 degrees Celsius above seasonal averages, according to Yonhap NewsTV.
Morning Fog and Air Quality Advisories
Drivers facing early commutes need to exercise caution due to thick morning fog blanketing various regions. Daytime conditions feature strong sunlight, driving ultraviolet radiation levels to “very high” categories across southern provinces, while parts of the Seoul metropolitan area and South Chungcheong Province experience “bad” ozone concentration levels, according to Yonhap NewsTV forecasts.
Coastal Conditions and Chuseok Holiday Outlook
Marine conditions remain hazardous, with gale and high-seas warnings active across the East Sea and South Sea. Wave heights reach up to 3.5 meters, accompanied by strong winds battering the Gyeongsang coastline. Looking ahead to the Chuseok holiday, forecasters predict generally cloudy skies across the country, with rain forecast for southern regions and Jeju Island on Saturday.
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