Temperatures near seasonal average Monday; showers expected across Greater Seoul, inland areas

Most of the country will see daytime highs stay below 30 degrees Celsius on Monday, as high pressure moving eastward from near the Bohai Sea keeps temperatures near seasonal norms. Jeju, however, will be an exception: a trough approaching from near Shanghai is expected to bring rain from the morning through the night, with 20 to 60 millimeters of precipitation forecast.

Showers are also expected to develop across parts of Greater Seoul and other inland areas between the afternoon and evening, with 5 to 40 millimeters forecast for the metropolitan area and around 5 to 30 millimeters elsewhere inland. Forecasters attribute the showers to atmospheric instability caused by cold air in the mid-to-upper atmosphere meeting warmer surface air heated by daytime sun. Northern Gyeonggi Province and the central and northern inland areas and mountains of Gangwon Province face a heightened risk of hail or graupel due to stronger instability, and residents are urged to take precautions against weather-related accidents.

Morning lows Monday will range from 16 to 21 C, with afternoon highs of 21 to 28 C — similar to or slightly below typical levels for this time of year. By city, morning lows and afternoon highs are forecast as follows: Seoul, 20 and 28; Incheon, 20 and 27; Daejeon, 19 and 27; Gwangju, 21 and 25; Daegu and Busan, 19 and 24; Ulsan, 18 and 23.

Ozone concentrations in Greater Seoul — excluding northern Gyeonggi Province — and South Chungcheong Province are expected to reach "poor" levels in the afternoon. High ozone levels can irritate the skin and respiratory system, and health authorities advise limiting strenuous outdoor activity during afternoon hours.

At sea, strong winds of 9 to 18 meters per second and waves of 1.5 to 4 meters are forecast on the East Sea through Monday. Swells will continue to push toward the eastern coast for now, with waves likely to wash over breakwaters and rocky shores in some areas. Authorities are urging the public to stay away from the coastline and to secure small vessels and other waterfront facilities.