Most parts of the country were hit by a severe cold wave early Wednesday morning, with South Korea's weather service issuing a cold wave advisory for the third consecutive day.

As of 5 a.m., temperatures had dropped to minus 13.9 degrees Celsius in Seoul, minus 18.3 degrees in Paju, minus 11.6 degrees in Suwon, minus 12.1 degrees in Incheon and minus 17.2 degrees in Chuncheon, Gangwon Province.

The mercury also dropped below zero in the central and southern parts of the country, with minus 11.8 degrees Celsius in Cheongju, North Chungcheong Province; minus 9.5 degrees in Jeonju, North Jeolla Province; minus 6 degrees in Gwangju; minus 8.5 degrees in Daegu; and minus 6.4 degrees in Busan.

The weather agency issued cold spell alerts or warnings for most of the nation -- Seoul, Incheon, the Chungcheong region, Gangwon and the northern part of Gyeonggi.

"A very cold, high pressure system from northern China is exerting influence over the Korean Peninsula, causing temperatures to drop sharply," the KMA said. It said such conditions may last for some time.

The agency said besides the advisory, it has issued more severe "cold wave warnings" for 27 cities and counties in the northern Gyeonggi and Gangwon provinces. It said a warning is also in effect for Jecheon, a mountainous part of North Chungcheong Province.

The KMA issued its first "cold wave advisory" on Monday for the Seoul region this winter as temperatures dropped way below freezing.

A cold wave advisory goes into effect if the mercury drops by more than 10 degrees compared with the previous day and if early morning lows drop below minus 12 degrees Celsius for two straight days.

A cold wave warning is issued if the temperature drops more than 15 degrees vis-a-vis the previous day and if morning lows fall below minus 15 degrees Celsius for two consecutive days.

Later in the day, the KMA said a total of 23 cold wave advisories have been issued so far this month, the second most advisories issued in January from 2005-2014.

But the number of advisories will likely increase as the present cold spell is expected to continue through next week, a weather agency official said.

Over the 10-year period, cold wave advisories were issued most in January, with a total number of 183, an average 18 times every January.

During the same period, cold advisories were issued 175 times in December, 61 times in February, 33 times in November, 23 times in March and nine times in October, according to the official. (Yonhap)