The season's first ice was observed on the Baengnokdam Crater Lake at the top of Halla Mountain on Jeju Island Tuesday morning as the area experienced subzero temperatures for the second day.

According to the Jeju branch of the Korea Meteorological Administration(KMA), the morning low at the crater lake, measured by an automatic weather station, recorded minus zero-point-three degrees Celsius, following Monday’s minus one-point-five degrees.

The KMA attributed the plunge in mercury levels to cold air that advanced southward after a low pressure front moved north.

Frost or ice observed on Mt. Halla are not official indicators in determining the early or late arrival of a season. However, last year, the first hoarfrost on Halla was detected on October 17, making this year's first freeze about six days faster.