Korea's extreme summer: 42.5 C heat, record downpours — and now, finally, autumn

This summer's nationwide average temperature ranked third-highest on record amid a season marked by extreme heat topping 39 degrees Celsius and record-breaking downpours.

The Korea Meteorological Administration released its analysis of summer 2026 (June–August) climate characteristics and causes on Thursday.

The national average temperature this summer was 25.4 C, 1.7 degrees above the seasonal norm — trailing only 2025 (25.7 C) and 2024 (25.6 C) in the historical record.

More striking than the average, however, was the sheer intensity of individual heat events. Temperatures began climbing in earnest in mid-July, and from late July through early August, the combined influence of the North Pacific High and the Tibetan High kept the heat relentless around the clock.

The most severe stretch ran from July 28 to Aug. 3, centered on South Gyeongsang Province. Strengthening westerly winds combined with topographic effects drove the province's daily maximum temperature to an all-time record for seven consecutive days. On Aug. 2, the mercury in Yangsan, South Gyeongsang Province, soared to 42.5 C.

The number of days reaching 39 C or above was also unprecedented. Across 83 Automated Surface Observing System stations this year, temperatures hit 39 C or higher on 42 occasions — the most since 2010 and surpassing the previous record of 38 set in 2018.

In early August, the heat's epicenter shifted westward toward the Greater Seoul area. Hot, humid air flowing in from a tropical depression that had weakened from Typhoon Dolphin pushed temperatures sharply higher. The national average temperature during that period reached 29.1 C, the highest ever recorded for early August.

Nights offered little relief. The nationwide average number of tropical nights this summer reached 18.2 days — about 2.8 times the seasonal norm of 6.5 days and the second-highest total on record. Tropical nights exceeded 30 days in western regions, along the South Sea coast, in Jeju and in major cities. Eleven stations — including Gwangju, Namwon, Wando and Gumi — logged their highest-ever tropical night counts since records began.

The seas were no exception. The average sea surface temperature in waters surrounding the Korean Peninsula this summer was 24.3 C, the highest in the past decade. The South Sea hit 25.4 C, a ten-year high, while the East Sea and the West Sea ranked second and third highest, respectively, over the same period. Late-August sea surface temperatures also reached 28.0 C, the highest in a decade.

Despite the intense heat, total summer rainfall came in below normal. Nationwide precipitation reached 558.6 millimeters, just 76.1 percent of the seasonal average of 727.3 mm. The number of rainy days also fell short at 31.2, some 7.3 days below normal — the third consecutive summer since 2024 in which rainfall has trailed the seasonal average.

Regional disparities were pronounced even during the monsoon season. This year's rainy season began June 30 in Jeju and southern regions and July 1 in central regions — later than usual. The stationary front's influence was concentrated mainly over central Korea, leaving the south and Jeju relatively dry. Total monsoon-season precipitation nationwide was 218.6 mm, only 60.3 percent of the seasonal norm.

Southern regions were also hit by drought. South Gyeongsang Province in particular recorded 48.2 meteorological drought days over the summer — the most of any region nationwide and the sixth-highest on record.

When rain did fall, it fell hard. From mid-August onward, locally record-breaking downpours struck. A low-pressure system approaching from near Shanghai, China, brought heavy rain to the South Gyeongsang coast from Aug. 15 to Aug. 18. On Aug. 17, Geoje received 124.5 mm of rain in a single hour. That day, Geoje's total daily precipitation reached 654.3 mm — the third-highest single-day total ever recorded there.

Over four days from Aug. 15 to Aug. 18, Geoje received 968.1 mm of rain — surpassing the city's entire summer seasonal average of 935.1 mm in just four days, and equivalent to roughly half its average annual precipitation.

Heavy rain continued at the end of August as well, centered on the Chungcheong and Jeolla regions. On Monday and Tuesday, Boseong and Yeonggwang in South Jeolla Province recorded rainfall exceeding 100 mm per hour.

Korea Meteorological Administration Commissioner Lee Mi-seon said this summer again saw extreme climate events — heatwaves, heavy rain and drought — while climate volatility increased and the risks of regional polarization and compound disasters became more pronounced. She said the agency had worked to strengthen its weather services for disaster preparedness by introducing new alert categories, including a major heatwave warning, a tropical night advisory and an emergency alert text for catastrophic rainfall.