On Thursday, the morning temperatures in South Korea are forecasted to drop to below freezing, coupled with a significant temperature difference that could reach as high as 20 degrees during the day. The National Weather Service has reported that, particularly in the inland regions, temperatures will likely be below 0 degrees Celsius early in the day, with daytime highs ranging from 8 to 16 degrees Celsius depending on the location. Major cities such as Seoul and Incheon are expected to experience daytime highs of 11 and 8 degrees respectively.

Additionally, the weather report warns of dense fog in various parts of the inland areas, including southeastern Gyeonggi, inland Gangwon, and inland North Jeolla, reducing visibility to under 200 meters in some areas. This may cause disruptions in air traffic, and the public is advised to check flight information ahead of time. Meanwhile, there might be light rain in southern coastal areas of Gangwon, adding to the day's variable weather conditions and reminding residents to be cautious while traveling.

Air quality levels are predicted to be 'normal' across the country, but caution is advised in Sejong and Chungbuk as well as in Daegu and Gyeongbuk, where air quality may drop to 'bad' levels during early morning hours. Overall, citizens are encouraged to stay informed about the daily weather and air quality updates to ensure safety and health during these fluctuating conditions.