South Korea’s mild autumn conditions will give way to colder temperatures on Friday, as mercury nationwide drops.

Dense fog with visibility below 200 meters is expected to arrive early in the morning across the Chungcheong region and southern inland areas.

Stagnant air will push fine dust levels to “bad” in parts of the southeast through the morning.

Morning lows will fall to between minus one and nine degrees Celsius, up to four degrees colder than Wednesday's.

Daytime highs will range from 12 to 19 degrees, amid a continued 15-degree swing between day and night.

Waves of up to three meters are forecast in the East Sea and waters off Jeju.