Record Heatwave Grips East Asia: Japan and South Korea Shatter Temperature Records
East Asia is in the grip of an unprecedented heatwave, with Japan and South Korea experiencing record-breaking temperatures that have left authorities scrambling to protect public health and infrastructure. The summer of 2025 has brought not only the hottest days on record for both countries but also a string of sweltering nights, straining hospitals and raising urgent questions about the impact of climate change on the region.
On July 30, Japan recorded its highest temperature ever: 41.2 degrees Celsius (106.16 degrees Fahrenheit) in Tamba, Hyogo Prefecture. Meanwhile, South Korea endured a record 22 consecutive “tropical nights” in July, with overnight temperatures in Seoul not dipping below 25 degrees Celsius (77 degrees Fahrenheit) for over three weeks—a phenomenon unseen since modern records began in 1907. The heatwave has already claimed dozens of lives and sent tens of thousands to hospitals, with the elderly and vulnerable populations at particular risk.
How Did the Heatwave Unfold?
The heatwave’s onset was both sudden and intense. In Japan, the meteorological agency reported that on July 30, temperatures soared past 35 degrees Celsius at 271 of its 914 observation points, with new highs set in 39 locations. Kyoto, a city famed for its historical sites and tourism, reached 40 degrees Celsius for the first time since records began in 1880. The previous national record of 41.1 degrees Celsius, set in 2018 and matched in 2020, was surpassed.
South Korea faced its own extremes. The Korea Meteorological Administration (KMA) confirmed that Seoul’s overnight low on July 30 was 29.3 degrees Celsius, marking the 22nd consecutive “tropical night.” The KMA defines a tropical night as one where temperatures remain above 25 degrees Celsius from 6:01pm to 9am the next day. The previous July record was 21 such nights, set in 1994. In some regions, daytime highs neared 40 degrees Celsius, with Anseong in Gyeonggi Province hitting 40.6 degrees on July 27.
Youn Ki-han, director of Seoul’s meteorology forecast division, explained the phenomenon:
“Normally, if it’s hot for just a day, temperatures spike and then quickly return to normal. But when warm conditions persist for several days, the heat doesn’t fully dissipate—it lingers and accumulates with each day.”
Disrupted Monsoon Patterns and Early Heat
Adding to the crisis, the traditional East Asian monsoon season has become increasingly unpredictable. Historically, the rainy season brought relief from the summer heat, but this year, both South Korea and Japan saw shorter and less intense monsoons. In western Japan, the rainy season ended in late June—the earliest since records began. In South Korea, the monsoon was so brief and sporadic that many residents stopped carrying umbrellas, despite forecasts.
Scientists attribute these disruptions to climate change, which is altering atmospheric patterns and making extreme weather events more frequent and severe. As a result, the region is experiencing not just hotter days, but also warmer nights and erratic rainfall, compounding the risks to agriculture, water supplies, and public health.
Impact on Health and Society
The human toll of the heatwave has been severe. In Japan, more than 10,800 people were hospitalized with heatstroke and other heat-related illnesses in the week leading up to July 21—the highest weekly figure so far this year. Sixteen people died during that period, with the majority of victims aged over 64. The Fire and Disaster Management Agency issued heatstroke alerts for 33 of Japan’s 47 prefectures, urging residents to stay indoors, use air conditioning, and remain hydrated.
South Korea has also seen a sharp rise in heat-related illnesses and deaths. At least 16 people have died from suspected heatstroke so far this year, triple the number from the same period in 2024. Hospitals have reported a surge in admissions, and authorities have issued repeated warnings to avoid outdoor activities during peak heat hours.
The elderly, children, and outdoor workers are especially vulnerable. The government has opened cooling centers and distributed water and fans to at-risk populations. In Seoul, officials have even offset water bills to encourage residents to run their air conditioners, highlighting the extraordinary measures being taken to cope with the crisis.
Strain on Infrastructure and Daily Life
The heatwave has placed immense pressure on infrastructure. Electricity demand has soared as millions rely on air conditioning, raising concerns about potential blackouts. Transportation systems have faced disruptions, with train tracks and roads at risk of buckling under the extreme heat. In rural areas, farmers are struggling to protect crops from heat damage and drought, with reports of premature fruit drop and sun-scorched vegetables in places like Jeju Island.
Tourism, a major economic driver in cities like Kyoto, has also been affected. The city, which welcomed a record 10.88 million foreign visitors last year, saw temperatures hit 40 degrees Celsius for the first time on record. Tourists and locals alike have been urged to avoid outdoor sightseeing during the hottest parts of the day.
Climate Change: The Driving Force Behind Extreme Heat
Scientists overwhelmingly agree that human-driven climate change is amplifying the frequency and intensity of heatwaves worldwide. The World Meteorological Organization (WMO) reported that Asia is warming nearly twice as fast as the global average. The average temperature of Asia’s landmass last year was about 1.04 degrees Celsius above the 1991-2020 trend, making 2024 either the warmest or second warmest year on record, depending on the dataset.
June 2025 was the third-warmest June globally since records began in 1850, according to NOAA, NASA, and the Copernicus Climate Change Service. Europe and Asia both experienced their fifth-warmest June, while the world as a whole saw a string of heat records broken across continents. The WMO warns that extreme heat is now a daily reality for millions and describes it as a “silent killer,” with modelled estimates showing around 489,000 heat-related deaths annually between 2000 and 2019, mostly in Asia and Europe.
The WMO and the United Nations have called for urgent action to address the growing threat of extreme heat. Initiatives include improving early warning systems, developing heat-health action plans, and strengthening international cooperation to protect vulnerable populations. Scaling up heat health-warning systems in 57 countries could save an estimated 98,314 lives per year, according to recent studies.
Regional and Global Context
The heatwave in East Asia is part of a broader pattern of extreme weather in 2025. The Mediterranean and Balkans are enduring their third heatwave of the summer, with wildfires forcing evacuations and causing casualties. North Africa and the Middle East have seen severe disruptions to electricity and water supplies, while the United States has faced prolonged heatwaves with heat index values reaching 43-46 degrees Celsius. Even Scandinavia has not been spared, with Finland experiencing more than 15 days above 30 degrees Celsius and Norway and Sweden facing extreme forest fire risks.
In Asia, the crisis is particularly acute. China’s National Climate Centre reported a record number of days with temperatures above 35 degrees Celsius since mid-March. India issued a red alert for New Delhi after the heat index hit 51.9 degrees Celsius in June. Myanmar experienced its hottest April day ever, with the mercury reaching 48.2 degrees Celsius in Chauk.
Why Are Nights Getting Hotter?
One of the most alarming aspects of the current heatwave is the persistence of high overnight temperatures, known as “tropical nights.” These nights offer little respite from the daytime heat, preventing the human body from recovering and increasing the risk of heat-related illnesses. The phenomenon is particularly dangerous for the elderly, those with chronic illnesses, and people without access to air conditioning.
According to the Korea Meteorological Administration, the number of tropical nights in Seoul this July broke a 117-year record. The lack of cooling at night is linked to a combination of factors, including urban heat island effects (where cities retain heat due to concrete and asphalt), high humidity, and broader shifts in atmospheric circulation caused by climate change.
Experts warn that as global temperatures rise, tropical nights will become more common, exacerbating health risks and placing further strain on energy systems. The WMO emphasizes the need for cities to adapt by increasing green spaces, improving building insulation, and investing in public cooling infrastructure.
Adapting to a Hotter Future
Governments in Japan and South Korea are taking steps to adapt to the new reality of extreme heat. Both countries have launched public awareness campaigns, distributed cooling equipment, and expanded access to emergency medical care. The focus is on protecting the most vulnerable—especially the elderly, children, and outdoor workers.
International organizations are also stepping up. The Global Heat Health Information Network, in partnership with the WMO and the UN Office for Disaster Risk Reduction, has launched new resources to help countries strengthen their heat risk reduction strategies. These include assessments of heat action plans, case studies in heat resilience, and guidance on best practices for governance and innovation.
However, experts caution that adaptation alone is not enough. The root cause—rising greenhouse gas emissions—must be addressed through aggressive mitigation efforts. The WMO and UN are urging countries to limit global temperature rise to 1.5 degrees Celsius above pre-industrial levels, in line with the Paris Agreement, to avoid the most catastrophic impacts of climate change.
In Summary
- Japan and South Korea are experiencing record-breaking heatwaves, with Japan hitting 41.2°C and Seoul enduring 22 consecutive tropical nights.
- The heatwave has led to a surge in heat-related illnesses and deaths, particularly among the elderly and vulnerable.
- Disrupted monsoon patterns and persistent high temperatures are linked to human-driven climate change.
- Authorities are implementing emergency measures, but experts warn that adaptation must be paired with aggressive action to reduce greenhouse gas emissions.
- The crisis in East Asia is part of a global pattern of extreme heat, highlighting the urgent need for coordinated international action.
