On the 23rd, which is Cheoseo on the seasonal calendar and a Sunday, the heat will continue across most of the country, with daytime highs rising to 35 degrees. Rain will fall in the Seoul metropolitan area and Gangwon through early morning, and from the afternoon there will be places, mainly in western regions, that see showers accompanied by gusty winds and thunder and lightning.
According to the Korea Meteorological Administration on the 22nd, the country will be mostly cloudy at times on the 23rd. Morning lows are forecast at 22–26 degrees, with daytime highs at 31–35 degrees. With heat advisories issued mainly for the Chungcheong region, the southern regions, and Jeju, the apparent high in most regions nationwide will climb to around 33 degrees for the time being. In parts of Jeolla, Gyeongnam, and Jeju, the apparent temperature is expected to rise to around 35 degrees.
There will be places that experience tropical nights, with overnight lows staying at or above 25 degrees because temperatures do not drop enough during the night. In areas with showers, temperatures will briefly fall, but after the rain stops, temperatures are expected to rise again amid high humidity.
Rain will continue mainly in the Seoul metropolitan area and Gangwon through the early morning of the 23rd. Expected rainfall is 5–60 millimeters in Seoul, Incheon, Gyeonggi, and the inland and mountainous areas of Gangwon, and 5–40 millimeters on the east coast of Gangwon. In the afternoon, showers will fall in western North Jeolla and the mid-mountain and mountainous areas of Jeju. Showers are also expected in southern and northeastern Gyeonggi and in South Chungcheong from afternoon to evening. Expected rainfall is 5–40 millimeters in southern and northeastern Gyeonggi, South Chungcheong, and western North Jeolla, and 5–30 millimeters in Jeju's mid-mountain and mountainous areas.
In areas with rain or showers, thunder and lightning may occur along with gusty winds. Caution is needed as rainfall can vary greatly even within the same area. From early morning to morning, fog with visibility below 1 kilometer may form mainly in the central region and the inland areas of North Jeolla and North Gyeongsang. Fog can be thicker on coastal bridges and roads near rivers, lakes, and valleys.
At sea, strong winds and waves of 2–4 meters will prevail through the 24th mainly in the far southern West Sea, the waters off Jeju, and the outer far seas of the eastern South Sea. For the time being, strong swells will move into the South Jeolla coast, the southern coast of Gyeongnam, and the Jeju coast, with high waves overtopping rocky shores and breakwaters in some places.