Jeju in December:
chilly, rain here and there

The winter monsoon settles over the north coast, bringing grey days and the odd snow flurry. Once snow builds up on Hallasan, the mountain roads are often open only to cars with chains or other winter gear, which matters if you rent a car. The Seongsan Sunrise Festival at Seongsan Ilchulbong centres on a countdown on the night of December 31 and the first sunrise on January 1.

Days averaged 11°C and nights 6°C, cool enough that outdoor sightseeing called for a layer. Out of 31 days, about 9 brought rain; the rest stayed dry. The driest year, 2021, had 4 rain days; the wettest, 2023, had 15.

With as little as 10.0 hours of daylight, the sightseeing day was short and dinner came after dark. Nights fell below 5°C on 14 days on average. December 2025 averaged 13.2°C by day, 2.1°C above the 20-year mean. The lowest night on record was −1°C in 2010.