Japan Hits 41.2C as Seoul's Record Hot Nights Deepen East Asia's Heat Crisis

Record Days and Relentless Nights Put Millions Under Strain

Japan recorded its highest temperature ever on July 30, 2025, when Tamba in Hyogo Prefecture reached 41.2 degrees Celsius (106.16 degrees Fahrenheit). In South Korea, Seoul endured its 22nd consecutive tropical night in July, with temperatures staying above 25 degrees Celsius (77 degrees Fahrenheit) overnight for more than three weeks.

The records capture two sides of the same emergency: dangerous daytime heat and nights that offer little chance to recover. Across the two countries, the summer heat has claimed dozens of lives, sent tens of thousands of people to hospitals and placed particular pressure on older residents and other vulnerable groups.

Japan's previous national temperature record was 41.1 degrees Celsius, set in 2018 and matched in 2020. The new high in Tamba came during a much wider surge in temperatures. On July 30, readings exceeded 35 degrees Celsius at 271 of the country's 914 observation points, while 39 locations registered new highs.

Kyoto reached 40 degrees Celsius for the first time since its records began in 1880. Seoul's July run of tropical nights was unprecedented in modern records stretching back to 1907, exceeding the previous July record of 21 nights set in 1994.

As of July 31, authorities were responding with health warnings, cooling centres, water and fans, while hospitals faced rising demand. Electricity supplies, transport, farming and tourism were also under pressure. Shorter and less reliable rainy seasons had reduced the relief that residents traditionally expect before the height of summer.

How the Heat Built Across Japan and South Korea

Japan's July 30 readings show that the heat extended far beyond the location of the national record. Nearly three in every 10 observation points exceeded 35 degrees Celsius, based on the meteorological agency's figures of 271 out of 914 stations.

South Korea also experienced extreme daytime temperatures. Anseong, in Gyeonggi Province, reached 40.6 degrees Celsius on July 27. In Seoul, the overnight low on July 30 was 29.3 degrees Celsius, leaving residents with little relief even during the coolest hours.

The main developments unfolded over several weeks:

• Late June: The rainy season ended in western Japan, the earliest finish since records began.
• The week leading up to July 21: More than 10,800 people in Japan were hospitalised with heatstroke and other illnesses related to heat, and 16 died.
• July 27: Anseong in South Korea reached 40.6 degrees Celsius.
• July 30: Tamba set Japan's national record at 41.2 degrees Celsius, while Kyoto reached 40 degrees Celsius for the first time.
• July 30: Seoul recorded an overnight low of 29.3 degrees Celsius and its 22nd consecutive tropical night in July.

Japan and South Korea faced a combination of individual temperature records and prolonged exposure. The persistence matters for daily life: residents must manage the heat through successive afternoons and nights, rather than waiting for a brief hot spell to pass.

Why Seoul's Tropical Nights Are So Dangerous

The Korea Meteorological Administration (KMA) defines a tropical night as one when temperatures remain above 25 degrees Celsius from 6:01pm until 9am the following morning. Seoul's July 30 overnight low was 4.3 degrees above that threshold.

Youn Ki-han, director of Seoul's meteorology forecast division, explained how heat accumulates when warm conditions continue for several days:

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.

Warm nights prevent the human body from recovering from daytime heat, increasing the danger of illnesses related to high temperatures. Older people, those with chronic illnesses and residents without air conditioning face particular risks.

Seoul's July total broke a record described as standing for 117 years. The persistent warmth is linked to several factors working together: high humidity, changes in atmospheric circulation associated with climate change, and the urban heat island effect.

Concrete and asphalt retain heat, helping cities stay warm after sunset. This is the urban heat island effect: streets and buildings hold onto warmth that would otherwise escape more readily. When that retained heat combines with humid air and already high temperatures, overnight cooling becomes harder.

As global temperatures rise, tropical nights are expected to become more common, adding to health risks and demand for electricity. The World Meteorological Organization (WMO) has called for more green spaces, better building insulation and public cooling infrastructure to help cities adapt.

A Shorter Rainy Season Removes Summer Relief

Western Japan's rainy season ended in late June, earlier than in any previous year on record. South Korea's monsoon was also brief and sporadic. Rain became so unreliable that many residents stopped carrying umbrellas despite forecasts.

The East Asian monsoon has traditionally brought relief from summer heat. In 2025, shorter and less intense rainy seasons in both countries left communities facing prolonged warmth with fewer breaks.

Scientists link these disruptions to climate change, which is altering atmospheric patterns and making extreme weather more frequent and severe. The changes combine hotter days, warmer nights and erratic rainfall, placing additional pressure on agriculture, water supplies and public health.

For farmers and city residents alike, the problem extends beyond the highest temperature of a particular afternoon. Unreliable rain and sustained heat can continue to affect crops, water needs and household routines throughout the season.

Hospitals Face Rising Illness and Deaths

Japan recorded more than 10,800 hospitalisations for heatstroke and other illnesses related to heat in the week leading up to July 21. It was the highest weekly figure of the year so far. Sixteen people died during that period, and most victims were older than 64.

The Fire and Disaster Management Agency issued heatstroke alerts for 33 of Japan's 47 prefectures, covering roughly seven in every 10 prefectures. Residents were urged to stay indoors, use air conditioning and remain hydrated.

South Korea had recorded at least 16 deaths from suspected heatstroke so far in 2025, triple the number during the same period in 2024. Hospitals reported a surge in admissions, and authorities repeatedly warned residents to avoid outdoor activities during the hottest hours.

The Japanese and South Korean death figures cover different periods: Japan's 16 deaths were recorded within the week leading up to July 21, while South Korea's figure covered the year to date. Both show the health burden already accompanying the sustained heat.

Older people, children and outdoor workers are among those most exposed. Governments have opened cooling centres and distributed water and fans to vulnerable residents. In Seoul, officials have also offset water bills as part of efforts to encourage residents to run their air conditioners.

Electricity, Transport and Farming Come Under Pressure

Air conditioning has become essential for millions of households during the heatwave, driving up electricity demand and raising concerns about possible blackouts. Warm nights extend the period when people need cooling beyond the afternoon peak.

Transport systems have also faced disruption, with roads and railway tracks at risk of buckling in extreme heat. The pressure on infrastructure adds another difficulty for communities already trying to reduce exposure outdoors.

Farmers are struggling to protect crops from heat damage and drought. In places including Jeju Island, fruit has dropped prematurely and vegetables have been scorched by the sun. Erratic rainfall adds to the challenge of keeping crops supplied with water.

Kyoto's first recorded temperature of 40 degrees Celsius has brought the heat emergency into one of Japan's major tourism destinations. The city welcomed a record 10.88 million foreign visitors in 2024, making the conditions a concern for large numbers of travellers as well as residents.

Visitors and local people have been urged to avoid outdoor sightseeing during the hottest parts of the day. For a city known for its historic sites, the heat changes when people can comfortably spend time outside and how they plan their visits.

Asia's Warming Gives the Records a Wider Context

The WMO reported that Asia is warming nearly twice as fast as the global average. In 2024, the average temperature across Asia's landmass was about 1.04 degrees Celsius above the 1991 to 2020 reference level.

Depending on the dataset, 2024 was either Asia's warmest or second warmest year on record. The different rankings reflect the datasets used, while both place the year among the region's hottest.

Scientists overwhelmingly agree that climate change driven by human activity is increasing the frequency and intensity of heatwaves worldwide. Rising greenhouse gas emissions are the underlying cause identified in calls for stronger action to limit warming.

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 each experienced their fifth warmest June, while temperature records were broken across continents.

The WMO describes extreme heat as a "silent killer" and warns that it is now a daily reality for millions of people. Modelled estimates put annual deaths related to heat at about 489,000 between 2000 and 2019, with most occurring in Asia and Europe.

Those estimates show the scale of the health threat beyond the deaths recorded during a single heatwave. Japan and South Korea's current emergency is unfolding within a much broader rise in exposure to dangerous temperatures.

Other Regions Are Also Facing Extreme Heat

The Mediterranean and the Balkans were enduring their third heatwave of the summer, with wildfires forcing evacuations and causing casualties. North Africa and the Middle East faced severe disruptions to electricity and water supplies.

The United States experienced prolonged heatwaves with heat index values reaching 43 to 46 degrees Celsius. The heat index describes how hot conditions feel when temperature and humidity are considered together.

Scandinavia also faced unusual heat. Finland experienced more than 15 days above 30 degrees Celsius, while Norway and Sweden faced extreme forest fire risks.

Elsewhere in Asia, China's National Climate Centre reported a record number of days above 35 degrees Celsius since mid-March. India issued a red alert for New Delhi after the heat index reached 51.9 degrees Celsius in June.

Myanmar recorded its hottest April day ever when Chauk reached 48.2 degrees Celsius. Together, these events show how extreme heat has affected different parts of Asia and the wider world during the period surrounding Japan and South Korea's emergency.

Protecting People Now and Reducing Future Heat

Japan and South Korea have launched public awareness campaigns, distributed cooling equipment and expanded access to emergency medical care. Their immediate focus is on older people, children, outdoor workers and others most vulnerable to high temperatures.

The WMO and the United Nations have called for better early warning systems, heat health action plans and stronger international cooperation. Such plans organise warnings and protective measures so that communities can respond when dangerous temperatures are expected.

Studies cited in the response to extreme heat estimate that expanding heat health warning systems across 57 countries could save 98,314 lives a year. Warnings are one part of a wider effort that also includes access to cooling and support for vulnerable residents.

The Global Heat Health Information Network, working with the WMO and the UN Office for Disaster Risk Reduction, has launched resources to help countries strengthen their strategies for reducing heat risks. These include assessments of heat action plans, case studies on coping with heat, and guidance on governance and innovation.

Adaptation measures address the conditions people are already experiencing. Efforts to reduce greenhouse gas emissions address the cause of rising global temperatures. Experts warn that adaptation alone is insufficient, and that substantial emissions reductions are also needed.

The WMO and the UN are urging countries to limit the increase in global temperature to 1.5 degrees Celsius above levels before industrialisation, in line with the Paris Agreement, to avoid the most catastrophic effects of climate change. For Japan and South Korea, the immediate task remains protecting people through a summer already marked by national records and prolonged heat after dark.

Key Points

• Tamba reached 41.2 degrees Celsius on July 30, setting Japan's national temperature record.
• Seoul recorded its 22nd consecutive tropical night in July, with an overnight low of 29.3 degrees Celsius on July 30.
• Japan recorded more than 10,800 hospitalisations and 16 deaths in the week leading up to July 21.
• South Korea recorded at least 16 suspected heatstroke deaths in 2025, triple the number during the same period in 2024.
• Shorter rainy seasons, persistent overnight warmth and extreme daytime temperatures are adding pressure to health services, infrastructure and farming.
• Governments are expanding protective measures as the WMO and UN call for stronger heat warnings and reductions in greenhouse gas emissions.