The rain front will advance northward about five days earlier than in previous years, and Jeju will fall under the influence of a seasonal rain front on Friday with 5 mm to 20 mm of rainfall, the Korea Meteorological Administration predicted on Thursday.

The monsoon season will get under way in Jeju and the southern part of the country from June 18 to 20.

"The rain front, which is now far at sea south of Jeju, will temporarily advance northward, scattering rainfall on Jeju and some coastal regions in South Gyeongsang Province late at night," the KMA forecast. "It will retreat south on Saturday but will return to [the same area] from Monday."

The rain front is arriving five days later than last year, but four to five days earlier than average.

Midland regions including Seoul, eastern Gyeonggi Province, western Gangwon Province and northern Chungcheong Province will see sudden showers depositing 5 mm to 20 mm of rainfall with heavy winds, lightning and thunder on Friday afternoon.