(ATTN: UPDATES headline, lead, more info throughout with cold wave warning, heavy snow advisory; ADDS photo)
SEOUL, Jan. 6 (Yonhap) -- The Korea Meteorological Administration (KMA) issued cold wave and heavy snow alerts for most parts of the country Wednesday as the entire nation came under the grip of the season's coldest weather.
A cold wave warning went into effect for the whole of Seoul at 9 p.m. for the first time since Jan. 23, 2018. Mountainous areas of the southern island of Jeju also came under a cold wave warning for the first time since the nation introduced such alert systems in 1964.
A 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, followed by other areas Wednesday, including Incheon, west of Seoul.
Many other cities, including Daegu, have also issued a cold wave advisory, 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 weather agency also issued heavy snow advisories for Seoul, Jeju and almost all provinces of the country.
The advisory is issued for snowfall expected to exceed 5 centimeters in 24 hours.
Seoul received 3.8 centimeters of snow as of 9 p.m. The KMA said heavy snow is expected to fall until 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.
On Jeju Island, 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 in the island's coastal areas on the day.
Legislation on compensating virus-hit small biz picks up steam
Anger mounts over deepfake porn targeting Korean female celebs; more than 330,000 sign petition
Biden's pick for Asia policy likely to seek stronger regional alliances to check China
Iran's oil tanker seizure appears aimed at pressuring S. Korea to unlock frozen assets: experts
S. Koreans feel pinch of rising housing costs amid economic downturn