100-degree heat, 100 millimeters of rain: Korea's extreme weather, in numbers

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100-degree heat, 100 millimeters of rain: Korea's extreme weather, in numbers

Published: 26 Aug. 2025, 07:00 Updated: 26 Aug. 2025, 10:25

CHO JUNG-WOO
[email protected]

Audio report: written by reporters, read by AI

A passerby walks near Dongdaegu Station in Daegu shields themself from the sun with an umbrella on July 23. [YONHAP]

[BEHIND THE NUMBERS]

Korea is grappling with a summer of extremes, with blistering heat coinciding with bouts of torrential rain that dumped more than 100 millimeters an hour earlier in the season.

In early July, temperatures in Korea soared past 40 degrees Celsius (104 degrees Fahrenheit) in Gyeonggi's Gwangmyeong and Paju, cities just outside Seoul. It was the first time the country had ever seen July heat break that threshold. The national record, set in Hongcheon, Gangwon, in 2018, still stands at 41 degrees. The Korea Environment Institute noted in a report last month that 2018 remains the country’s hottest year on record.

“Heat waves are worsening droughts, and subsequent downpours are compounding damage to weakened soil, crops and infrastructure, which are evidence of the complex, cascading impacts of extreme weather,” the report said. “Such events are expected to recur annually, causing long-term, cumulative harm to infrastructure, agriculture and ecosystems.”

The string of record-breaking heat and rain prompted President Lee Jae Myung to order a review of the country’s disaster response system earlier this month, calling climate change “an imminent and central” item on the nation's agenda. The government has named climate adaptation and the transition to renewable energy its top priorities.

“These days, when it rains, it easily tops 100 millimeters [3.9 inches] an hour,” Lee told aides at a meeting on Aug. 14. “The climate crisis has become part of daily life.”

Amid the growing impact of climate change on extreme weather, the Korea JoongAng Daily examines the country's shifting summer weather patterns and its unfinished climate agenda through the numbers.

A passerby walks through Jung District in Daegu, holding a portable fan during a heat wave on Aug. 1. [NEWS1]

33 searing days

Korea has seen a high number of extremely hot days in recent years. Last year, the country endured 33 days of scorching temperatures. It marked the second most in the past decade, behind 2018, which saw 35 days.

As of Sunday, this year’s count has already reached 27, according to the Korea Meteorological Administration (KMA). With heat advisories blanketing much of the country, that number is expected to rise in the coming weeks.

Number of tropical nights and average summer temperature [YUN YOUNG]

The heat is lingering despite the passing of Cheoseo on Saturday, a seasonal marker in the lunar calendar that signals the retreat of summer heat. On Sunday, heat wave warnings were in effect for 182 of the nation’s 183 monitoring sites. Such alerts are issued when the heat index are forecast to stay at or above 33 degrees Celsius for at least two days.

The KMA attributes the sweltering conditions to the combined effects of the hot, dry Tibet High and the hot, moisture-laden North Pacific High.

Kim Baek-min, a professor of environmental atmospheric sciences at Pukyong National University, said in an interview with SBS radio last month that climate change is creating “favorable conditions” for these high-pressure systems to settle over the peninsula — a pattern that is likely to continue.

The North Pacific High forms when the sun heats the equator more than the poles, creating large-scale air circulation. The Tibet High develops when strong sunlight warms the high Tibetan Plateau, about 4 kilometers (2.5 miles) above sea level, causing the air to expand and create a strong high-pressure system.

A worker wipes sweat at a logistics center in Seoul during a heat wave on July 9. [NEWS1]

48 tropical nights

Heat has lingered long after sunset. In 2024, Korea endured 48 tropical nights — nights when temperatures remain above 25 degrees Celsius — the most since records began in 2015. This year, 41 such nights had already been recorded as of Sunday.

Seoul alone logged 23 tropical nights in July, breaking a century-old record. Meteorologists attribute the trend to overlapping high-pressure systems and hot winds trapped over mountain ranges, which prevent cooling at night.

The average summer temperature has also peaked last year, rising from 23.9 degrees Celsius in 2020 to 25.6 degrees.

Passersby and vehicles navigate a road submerged by heavy rain in Muan, South Jeolla, on Aug. 3. [NEWS1]

114 millimeters per hour

Korea’s total rainfall in 2024 measured 1,415 millimeters, close to the historical average. But its distribution has defied expectations.

February, one of the driest months, saw nearly triple its usual rainfall last year, which was the third-highest on record. August, normally the wettest month, received barely a third of its average rainfall. For the first time since 1973, February was wetter than August.

Summer rains overall were lighter than average, but far more concentrated. Nearly 79 percent of summer precipitation fell during the monsoon season, the highest share since records began. That kind of intensity has already led to disaster this summer. Parts of South Chungcheong were inundated when hourly rainfall peaked at 114 millimeters on July 17, submerging farmland the size of 28,000 soccer fields.

Experts say that such extremes, which are largely unpredictable, underscore the need for more diverse response systems that can be adapted more flexibly to different regions.

“We no longer have the capacity to keep building massive drainage systems and pumps to deal with unexpected extreme weather,” said Kim Yeo-won, an assistant professor at Korea University's Graduate School of Energy and Environment, noting the country’s limited land.

“What we need are smaller, more flexible systems — hybrid solutions that combine gray infrastructure with nature-based methods.”

Those might include green infrastructure such as rain gardens, which are designed to filter and absorb runoff by increasing soil permeability.

President Lee Jae Myung, far right, visits a town in Sancheong-eup, Sancheong, South Gyeongsang, to inspect damage from an extreme downpour on July 21. [JOINT PRESS CORPS]

Researchers warn that climate change is shifting Korea’s extreme summer downpours a month earlier. A study published in npj Climate and Atmospheric Science projected that storms delivering more than 30 millimeters an hour, once most common in August, will peak in July by the end of the century.

Even under low-emission scenarios, the frequency of such rainfall could double. If emissions continue rising, July downpours could be nearly four times as frequent.

“Disaster planning will need to be adjusted monthly, given that the downpours could take place earlier in the future,” said Postech professor Min Seung-gi, one of the lead researchers.

People cool off by dipping their feet in the Cheonggye Stream in central Seoul on Aug. 1. [YONHAP]

1.58 degrees

Korea’s coastal waters are warming rapidly. The National Institute of Fisheries Science reported that average sea surface temperatures reached 18.74 degrees Celsius last year, the highest since records began in 1968 and a sharp jump from 2023.

The warming has already reduced the ocean’s ability to support marine life. Primary productivity fell more than 21 percent in 2024, the institute said. It is known that a 1 degree rise in sea surface temperature increases precipitation by about 7 percent. Over the past half-century, Korean waters have warmed by 1.58 degrees, which is more than twice the global average.

40 percent

From earlier-than-usual heat waves to torrential downpours, Korea's summer of extremes highlights the country's growing vulnerability to climate change.

Korea’s domestic climate challenges coincide with its looming international obligations. Under UN rules, all countries committed to the Paris Agreement are required to update their emissions reduction targets, known as Nationally Determined Contributions (NDC), every five years.

In 2021, former President Moon Jae-in pledged to cut emissions 40 percent below 2018 levels by 2030 and enacted the Carbon Neutrality Act. Since then, however, Korea has not set targets beyond that year. The Constitutional Court ruled that the absence of reduction goals after 2031 violates the Constitution and ordered the government to amend the act by Feb. 28, 2026, to establish binding targets through 2049.

Rice paddies in Seogwipo, Jeju, crack from drought caused by a prolonged heat wave on July 8. [YONHAP]

This September marks the deadline for the 2035 NDC.

President Lee has pledged to align Korea’s 2035 climate target with its 2050 carbon neutrality commitment. Yet, with only weeks left before the September deadline, no draft has been released. Environment Minister Kim Sung-hwan told a special parliamentary committee on climate on Aug. 18 that a proposal would be unveiled next month, opened to public debate and finalized by late October.

For now, Korea remains among the world’s major emitters, alongside China and the European Union, that have yet to present their 2035 targets. As of this month, only 31 of the 195 countries have done so.

Influenced by the North Pacific High and the Tibet High, this year's peak summer weather began earlier and shows little sign of relenting. Rising coastal temperatures are one factor intensifying these conditions, heating the air and increasing its moisture content, which fuels heavier precipitation — a reminder of the cascading effects of a warming climate.

BY CHO JUNG-WOO [[email protected]]