Korea Meteorological Administration Announces Climate Analysis Results for This Summer… Record-High Temperatures
Hot Seas Trigger Early Expansion of North Pacific High, Leading to Early Heat
On August 5th, a construction worker in Daegu works under a parasol that provides shade from the sun. [Yonhap News Photo]
“(Seoul = Yonhap News) Reporter Lee Jaeyoung – The start of the ‘extreme summer’ was the hot sea,”
“One of the key reasons for the repeated heatwaves and heavy rain this summer, as announced by the Korea Meteorological Administration on the 4th, is the high sea surface temperatures of the North Pacific.”
National average temperature of 25.7°C, highest since 1973… Sea surface temperature 2nd highest in the past 10 years
Daily national average temperature this summer. [Provided by the Korea Meteorological Administration. Resale and DB prohibited]
“This summer, the national average temperature was 25.7°C, surpassing last year’s 25.6°C, making it the highest since 1973 when weather observation networks were expanded nationwide and set various weather record standards.”
“The average maximum temperature was 30.7°C, also the highest on record, and the average minimum temperature was 21.5°C, the second highest. There were 28.1 days of heatwaves (days with a maximum temperature of 33°C or higher), ranking third, and 15.5 days of tropical nights (nights with a minimum temperature of 25°C or higher), ranking fourth.”
“The surrounding seas of our country also recorded an average sea surface temperature of 23.8°C this summer, the second highest in the past 10 years (2016-2025) following last year’s 24.0°C.”
Heat started in late June and continued until August without the ‘Magic of Chuseo’
Essential parasols due to continued heatwaves
On August 5th, citizens are seen moving with parasols near Gwanghwamun Square in Jongno-gu, Seoul. [Yonhap News Photo]
“Last year, the heat started after the monsoon ended in late July, but this year it started from late June.”
“From June 29th to July 10th, the daily average temperature was the highest on record for the corresponding days except for July 4th. On July 8th, the midday temperature in areas like Gwangmyeong and Paju in Gyeonggi-do exceeded 40°C.”
“Tropical nights also started early, with the earliest occurrences recorded this summer at 21 weather observation points, including Daejeon (June 19th), Gwangju (June 19th), and Busan (July 1st).”
“The early heat resulted from the early expansion of the North Pacific High extending its influence southward over Korea. By late June, the North Pacific High covered Korea, ending the monsoon and bringing the hot weather.”
“The analysis suggests that the high sea surface temperatures of the North Pacific and the active convection in the tropical western Pacific caused the early expansion of the North Pacific High.”
“According to the Marine Climate Prediction Center, in June, the global average sea surface temperature was 0.4°C higher than the normal average (18.2±0.1°C), ranking third highest for June from 1995 to 2025. Particularly, the North Pacific and the tropical western Pacific were much hotter than usual, exceeding standard deviations by far.”
“The hot North Pacific became the ‘heat source’ for the expansion of the North Pacific High.”
“Additionally, active convection in the tropical western Pacific made the atmospheric high-pressure system over Korea and Japan develop more strongly than average.”
“If the strongly developed high pressures had quickly passed over Korea, the heat might not have been so severe. However, due to the appearance of the ‘CGT structure’ across the mid-latitudes of the Northern Hemisphere, they became stagnant. The CGT structure involves alternating high and low pressures from Western Europe to North America and is related to the strengthening of the Indian monsoon and convection in northwestern India.”
“Throughout late July and mid to late August, the sweltering heat persisted day and night.”
“From August 18th to 25th, the daily average temperatures ranked 1st to 2nd highest on record for the corresponding days.”
“Even after Chuseo (August 23rd), the typical cooling did not occur, negating the ‘magic of Chuseo.'”
“During this period, the Tibetan High expanded its influence, and in conjunction with the North Pacific High, covered Korea, causing heatwaves.”
“Especially in mid-August, as convection activity in northwestern India was again strengthened, the CGT structure reappeared, stagnating the high pressures and prolonging the heat.”
Monsoon ‘Disappears’… Overall Low Rainfall but 13 Instances of ‘100mm per Hour’ Downpours
Daily rainfall in average years and this summer. [Provided by the Korea Meteorological Administration. Resale and DB prohibited]
“This summer’s precipitation totaled 619.7mm, accounting for only 85.1% of the average summer precipitation (727.3mm).”
“The number of days it rained (precipitation days) was 29.3 days, 9.2 days fewer than the average, and the fifth fewest summer precipitation days since 1973.”
“This is because the North Pacific High expanded earlier than usual, starting the monsoon early, which ended very shortly thereafter.”
“This summer’s monsoon started on June 12th in Jeju and June 19th in central and southern regions, ending on June 26th and July 1st, lasting only 15 and 13 days, respectively, marking the second shortest monsoon season after 1973 (Jeju 7 days, central/southern regions 6 days).”
“Particularly in the Yeongdong region of Gangwon, experiencing meteorological drought since April 19th, this summer’s precipitation amounted to just 232.5mm, 34.2% of the average precipitation (679.3mm), with 24.7 rainy days, 18.3 days fewer than average, both setting record lows.”
“Due to the influence of the North Pacific High, southwesterly winds were frequent, resulting in less rainfall east of the Taebaek Mountains.”
“Winds become hot and dry as they cross mountains.”
On the morning of the 4th of last month, farmlands in the Eomdam area of Hampyeong-gun, Jeollanam-do, were submerged in rainwater. [Yonhap News Photo]
“While there was generally less rain, downpours occurred frequently.”
“From July 16th to 20th, a cold trough, along with cold air in the upper atmosphere, moved into Korea due to strengthened mid-latitude waves from the North Atlantic to East Asia but was blocked and could not escape due to the North Pacific High, resulting in very heavy rain ranging from 200mm to 700mm nationwide.”
“Additionally, from August 3rd to 4th, due to low-pressure effects in the south of Choongcheong, and from August 9th to 14th, hot and humid air flowing along the edge of the North Pacific High combined with cold air from a pressure trough in the upper atmosphere, forming a stationary front resulting in heavy rains in the Seoul metropolitan area, Yeongseo in Gangwon, and the southern coast.”
“Including records from Automatic Weather Systems (AWS), there were 13 instances of rainfall exceeding 100mm per hour this summer, occurring twice on July 17th and 20th each, four times on August 3rd, and five times on August 13th.”
jylee24@yna.co.kr