A bundled up chlid walks together with a mother in Seoul, Jan. 9. Yonhap

The season's coldest weather is likely to peak Friday with temperatures falling to as low as minus 21 degrees Celsius in parts of the country.

The morning low will range from minus 21 degrees to minus 5 degrees, which is lower than minus 14 degrees to minus 4 degrees on Thursday, according to the Korea Meteorological Administration (KMA).

In Seoul, the lowest temperature at 8 a.m. Thursday was minus 10.2 degrees and the lowest apparent temperature minus 16.7 degrees.

A cold wave advisory took effect for all of Seoul at 9 p.m. the previous day. An advisory is issued when a morning low of minus 12 degrees or less is expected for two or more consecutive days.

The lowest temperatures in other regions Thursday ranged from minus 16.9 degrees in the Daegwallyeong mountain pass in Gangwon Province to minus 13.6 degrees in Cheorwon and minus 13 degrees in Cheonan.

This photo shows icycles at Gangmun Beach in Gangneung, Gangwon Province, Jan. 9. Yonhap

Further south, temperatures fell to as low as minus 6.8 degrees in Gwangju, minus 6.1 degrees in Ulsan and minus 4.7 degrees in Busan.

"The temperature fell below minus 20 degrees in parts of the mountainous regions of Gangwon, while in the central region, the eastern area of North Jeolla Province and the northern inlands of North Gyeongsang Province, it ranged from minus 15 degrees to minus 10 degrees, and in the rest of the country it fell to minus 5 degrees," the KMA said.

"Many parts of the country recorded their lowest temperatures of this winter," it added.

The cold snap is expected to continue for some time, with Thursday's daily high forecast to range from 3 degrees to 11 degrees and most of the country seeing subzero temperatures all day.

The South Chungcheong and Jeolla provinces, as well as the mountainous areas of Jeju Island, are forecast to receive snow for the fourth consecutive day, with up to 5 centimeters of snow per hour at times.

Temperatures will return to average year levels on Sunday before dropping again toward the end of next week, though not to the same level as this week, the KMA said. (Yonhap)