Korea's rainy season arrives nationwide as heavy rain, strong winds hit Jeju, southern coast

Korea's monsoon season officially extended to the central regions Wednesday, bringing the entire country into the rainy season. A low-pressure system along a stationary front developed more intensely than forecast, with rain falling mainly across areas south of southern Chungcheong Province and spreading into the Chungcheong region, pulling central Korea into the monsoon zone.

According to the Korea Meteorological Administration, rain began in Jeju and the southern regions Tuesday, setting the official start of this year's rainy season as June 30 for those areas and Wednesday for the central regions. The start dates may be adjusted following further analysis, the agency said.

The rainy season arrived later than usual. For Jeju, it marks the third-latest start since 1973, while the southern and central regions each recorded their sixth-latest onset. The timing contrasts sharply with last year, when the monsoon began across most of the country in mid-June, underscoring how significantly the season's arrival can vary from year to year.

Heavy rain had been falling since Tuesday in Jeju, South Jeolla Province and the southern coast of South Gyeongsang Province.

Cumulative rainfall as of 8 a.m. Wednesday reached 222.0 millimeters at Hallasan's Jindallaebaht station on Jeju, 109.5 mm on Bogil Island in Wando-gun, South Jeolla Province, 95.0 mm in Seongsan-eup, Seogwipo, 74.2 mm in Gangjin-gun, South Jeolla Province, and 57.9 mm in Gwangju.

Rain is expected to continue in Jeju through the night, in Honam, southern North Gyeongsang Province and South Gyeongsang Province through the evening, and in southern Chungnam through midday.

Additional forecast rainfall totals are: 30–80 mm in Jeju excluding the northern section (up to 120 mm or more in mountainous areas); 20–60 mm in southern South Jeolla Province, Busan, the southern coast of South Gyeongsang Province and northern Jeju (up to 80 mm or more along the West Sea coast of southern South Jeolla Province and the southern coast of South Gyeongsang Province); 5–40 mm in Gwangju and northern South Jeolla Province; 5–30 mm in Ulsan and inland South Gyeongsang Province; 5–20 mm in southern North Jeolla Province; 5–10 mm in Daegu and southern North Gyeongsang Province; around 5 mm in northern North Jeolla Province; and less than 5 mm in Daejeon, Sejong, southern Chungnam and southern Chungbuk.

Jeju will also see gusts exceeding 70 kilometers per hour — 90 km/h in mountainous areas — while parts of the southern coast could experience gusts of around 55 km/h (15 meters per second).

At sea, winds of 30–60 km/h (8–16 m/s) and waves of 1.5–3.5 meters are expected through Wednesday night in the outer waters south of Jeju and the outer eastern waters of the South Sea. Wind and wave advisories may be issued for the remaining Jeju waters — excluding the northern inshore area — and the inner eastern South Sea as conditions are forecast to intensify.

Areas not affected by the monsoon rain — including Seoul, Incheon, northern Gyeonggi Province and the central and northern inland areas of Gangwon Province — can expect afternoon showers of 5–60 mm and 5–40 mm, respectively. The showers will be triggered by atmospheric instability as cold air in the upper atmosphere meets warm surface air heated by sunlight.

Inland areas without rain will see daytime temperatures climb above 30 degrees Celsius in many locations. Heat index values are expected to reach around 33 degrees in central inland areas and around 31 degrees elsewhere, making for a sweltering day.

Daytime highs across the country Wednesday are forecast to range from 22 to 33 degrees Celsius.

The KMA warned that rainfall zones and intensity could shift depending on the position of the stationary front and the development of low-pressure systems, urging the public to check the latest weather updates frequently. The agency particularly advised residents in areas expecting heavy rain — including Jeju and the southern coast — to prepare for low-lying flooding, river overflow and wind damage to structures, and to avoid outdoor activities near valleys and riverbanks where possible.