Jeju Has a climate that can be described either as humid subtropical or humid temperate. There is no dry season; it rains throughout the year. The wettest months are May - September. Summers are very warm, and winters are relatively cooler. The seasons of Jeju are as follows:
Spring: April - May: Temperatures are pleasant in the daytime and relatively low at night. Average low temperatures in April are 10.2 degrees Celsius. Average high temperatures in May are 21.6 degrees Celsius.
Summer: June to September: This is the wettest season. Temperatures rise steadily until August, reaching a peak of 30 degrees Celsius on average. September is cooler. Between July and September temperatures at night are as warm as day.
Autumn: October: Temperature and precipitation both begin t drop sharply, hovering between 15 and 21 degrees Celsius.
Winter:November to March: Temperatures drop steadily until January; the average daily mean is 5.3 degrees Celsius. It begins to get warmer in February.
All things considered, the best time to visit, is when it is not raining.