Geography of Korea: I. Natural Environment > 3. Climate > 6) Frost
Frost is formed when moisture-laden air comes into contact with a cold ground surface to form miniscule ice particles. The areas on the Korean Peninsula experiencing the earliest frost are Samsu and Kapsan on the Kaema Plateau in North Korea, where first frost arrives around September or October. Following this, frost first makes is appearance in Korea’s central interior and on the entirety of the Jinan Plateau in the south around October 10, with Busan receiving its first frost around December 20. The latest area to receive frost is Gosan on Jeju Island, which received its first frost around January 20.
Frost begins to disappear first in the south with the rising temperatures of spring. Gosan on Jeju Island, the last area to see frost, is also the first to see it go around January 30. Samsu and Kapsan have the longest period of frost, with it ceasing there around May 10. Frost persists on the Jinan Plateau until approximately the end of April.
The longer the frost-free period—the time between the last frost of spring and the first frost of fall—the more advantageous for agriculture. On the Korean Peninsula, areas with the shortest frost-free periods are Samsu and Kapsan, with around 120 days without frost. Conversely, at 350 days Gosan on Jeju Island has the longest frost-free period. The Jinan Plateau has a frost-free period of about 160 days, much briefer than that of surrounding regions.