Summer heat is just getting started as showers only add to the misery

South Korea has entered a full-blown heat wave as the country moves out of the monsoon season, with some regions forecast to see temperatures soar to 39 degrees Celsius and tropical nights expected to persist across much of the country.

The Korea Meteorological Administration said Monday that heat wave alerts are in effect across most of the country, with the maximum feels-like temperature expected to stay above 33 C nationwide and above 35 C in southern regions for now. Daytime highs are forecast to range from 31 C to 37 C.

Particularly intense conditions are expected in parts of Gwangyang in South Jeolla Province; Daegu (excluding Gunwi); North Gyeongsang Province's Gyeongsan, Cheongdo, Goryeong, Pohang and Gyeongju; and South Gyeongsang Province's Yangsan, Gimhae, Miryang, Uiryeong, Haman, Changnyeong and Hapcheon, where feels-like temperatures of 38 C or above, or actual highs of 39 C or above, are forecast. A major heat wave alert — a new category introduced this year — is in effect for those areas.

The heat wave has been driven by South Korea's position on the edge of the North Pacific High, which has allowed a steady inflow of hot, humid air. Cold air of minus 6 C or below sitting at an altitude of roughly 5 kilometers has destabilized the atmosphere, producing localized showers even amid the intense heat.

Showers of 5 to 60 millimeters are forecast Monday for the Greater Seoul area, Gangwon Province, northern North Chungcheong Province and northern North Gyeongsang Province. The Greater Seoul area and Gangwon Province could see particularly heavy bursts of 20 to 30 mm per hour from midday through the evening. On Tuesday, showers of 5 to 40 mm are expected across the Greater Seoul area, Gangwon Province, the Chungcheong region, and Daegu and North Gyeongsang Province.

The KMA said temperatures would drop temporarily while the showers fall, but warned that once the rain stops, heat and high humidity would quickly return, making conditions feel even more oppressive. Gusts, thunder and lightning may accompany the showers in some areas, and rainfall totals could vary significantly even within the same locality, the agency said.

The heat will not let up at night either. Tropical nights — when the overnight low stays at or above 25 C — are expected to persist across most of the country for now.

Heat-related illnesses are mounting as the heat wave continues. According to the Korea Disease Control and Prevention Agency's emergency room surveillance system for heat-related illness, 1,301 people had been treated for heat-related conditions as of Saturday. Six of those cases are suspected heat-related deaths, including two fatalities in Seoul over the past two months.

The KMA urged the public to take precautions, noting that feels-like temperatures at indoor and outdoor worksites, in rice paddies and on roads can run higher than those recorded at official weather stations. "Infants, the elderly and people with chronic illnesses should reduce outdoor activities and take care to stay hydrated and rested," the agency said.