A cold wave warning is set to be issued in Seoul on Wednesday for the first time in about three years, as the capital and central parts of the nation came under the grip of the season's coldest weather.

The Korea Meteorological Administration (KMA) said that the cold wave warning will take effect for the whole of Seoul at 9 p.m., marking the first such warning since the previous one was issued on Jan. 23, 2018.

The cold wave warning is issued when the morning low is below minus 15 C for more than two consecutive days, or when the temperature drops sharply and major damage is expected.

The warning was already issued for many areas in Gyeonggi, Gangwon, Chungcheong and North Gyeongsang provinces at 9 p.m. Tuesday, and the number of affected areas is expected to grow Wednesday.

Incheon, west of Seoul; many southern cities, including Daegu and Gwangju; and the southwestern provinces of Jeolla are to come under a cold wave alert, which is issued when the morning low is below minus 12 C for more than two days, by Wednesday night, the KMA said.

Morning lows in central regions fell below minus 15 C, with Seoul's daily lowest temperature at minus 12 C.

The KMA said snow will fall in Seoul between 6 p.m. and midnight, further pushing down temperatures later this week.

On Thursday, daytime highs will remain below minus 10 C in the greater Seoul area, while morning lows will further plummet to minus 17 C in Seoul and surrounding areas and minus 23 C in Chuncheon of Gangwon Province on Friday.

The KMA explained that the upcoming cold spell will be caused by a southward inflow of cold air from near Siberia. Temperatures will remain below the 30-year averages until next Tuesday and return to the seasonal averages next Wednesday, the KMA said.

Meanwhile, a cold wave warning is to be issued for mountain areas of Jeju Island, the southern resort island known for its balmy winter weather, at 9 p.m.

It will be the first time in 57 years that Jeju Island will come under a cold wave warning. The last such warning was issued on the island in 1964.

According to the KMA, temperatures are forecast to dip to around minus 10 C at the middle slopes of Mount Halla and minus 15 C near the top of the Jeju mountain on Thursday. The mercury will stay in the range of minus 2 C to 2 C on the island's coastal areas on the day.

A heavy snow advisory has already been issued for Jeju's mountain areas. (Yonhap)