Seoul: Heavy downpours are forecast to hit most of South Korea on Friday, including the central and southern regions and Jeju Island, marking the beginning of the year's monsoon season, the weather agency said.

According to Yonhap News Agency, the rain will spread to North Gyeongsang and South Gyeongsang provinces during the day, while the southern regions and Jeju may see the downpours ease throughout the day, as per the Korea Meteorological Administration (KMA).

The greater Seoul area and northern parts of Gangwon Province will receive heavy downpours of 30 to 50 millimeters per hour in the afternoon, whereas the rain will start falling at night for other parts of the province, as well as North Jeolla and South Chungcheong provinces.

The weather agency forecasted over 150 mm of rain to fall until Saturday in the greater Seoul area, parts of Gangwon Province, North Jeolla Province, South Chungcheong Province and Daejeon. Other regions, including southern Gyeonggi Province, North Chungcheong Province, South Jeolla Province and Gwangju, are anticipating more than 120 mm of rain during the same period.

The daily highs are expected to range between 23 to 31 C, with the heavy downpours bringing down temperatures slightly below the average.