Monsoon rains are forecast nationwide starting Thursday.

According to the Korea Meteorological Administration(KMA), the rainy season is projected to start with five to 20 millimeters of precipitation for the southernmost Jeju Island between late Monday and early Tuesday, one day later than the past average.

The rains are expected due to a low pressure system as part of a stationary front stretching from southern China to waters south of Japan.

The KMA had earlier projected monsoon rains to begin in the nation's southern regions starting Tuesday, but changed its forecast, citing the strong development of a northern high pressure system blocking the northward movement of the stationary front.

As a low pressure system from the west approaches the Korean Peninsula, heavy rains are in the forecast nationwide from Thursday afternoon to Friday.

The stationary front that causes heavy rainfall is predicted to travel south on Saturday as the monsoonal front will continue affecting Jeju and the south.