Climate Change Shortens Autumn
As the world grapples with the effects of climate change, Japan is experiencing an unusually prolonged summer, with September 2025 bringing record-breaking heat across the nation. The familiar saying, “Heat and cold last until the equinox,” seems to have lost its relevance this year, as temperatures continue to soar well past the autumnal equinox. This blog post explores Japan’s shifting seasons, the reasons behind the persistent heat, and what it means for the future of autumn, all while offering insights for an international audience curious about global climate trends.
A Swelteringly Unseasonal September
Japan’s September 2025 has been anything but typical. According to Mainichi Shimbun (September 13, 2025), average temperatures across most regions of Japan have exceeded the norm by over 2°C. In Tokyo alone, the number of “true summer days” (when the maximum daily temperature exceeds 30°C) reached a staggering 81 days this year, compared to the usual 50. This is the third consecutive year that Tokyo has seen over 80 such days, a trend that mirrors the climate of southern Kyushu, like Kagoshima, where 80 summer days are the norm.
Even international athletes competing in Japan have noted the unexpected intensity of the humidity. One remarked, “We prepared for the heat, but the oppressive humidity was beyond imagination” (Mainichi Shimbun, September 13, 2025). Forecasts from Weather Map (September 11, 2025) predict that temperatures will remain high for at least another month, with the period from September 13 to 26 expected to be particularly scorching. On September 14, Tokyo saw temperatures climb above 30°C before noon, signaling no immediate relief.
Why Is Autumn Delayed?
The prolonged heat can be attributed to two main factors: persistent high-pressure systems and unusually warm sea temperatures. High-pressure systems, typically associated with summer weather, have lingered over Japan, delaying the seasonal shift to cooler autumn conditions. Additionally, sea surface temperatures around Japan have risen significantly due to this summer’s extreme heat. As Weather Map explains, the warm ocean waters act like a giant bath, enveloping the Japanese archipelago in a steamy, humid environment that prevents cooler air from settling in.
This climatic shift is not just a quirk of 2025 but part of a broader pattern driven by climate change. Warmer oceans and altered atmospheric patterns are disrupting traditional seasonal cycles, pushing autumn further into the calendar year and shortening its duration.
The Shrinking Autumn and Its Impacts
Autumn in Japan is traditionally a season of crisp air, vibrant foliage, and clear skies—a time when locals and tourists alike flock to places like Hokkaido to witness the stunning red and gold hues of maple and ginkgo trees. However, as reported by Asahi Shimbun (September 13, 2025), Hokkaido’s iconic foliage season is showing signs of disruption. The prolonged heat is delaying the onset of autumn colors, and when cooler weather finally arrives, it may come too abruptly for trees to produce their usual vivid displays. Instead, leaves may fall prematurely, robbing the season of its signature beauty.
The shortened autumn also has broader implications. Farmers may face challenges as planting and harvesting schedules shift, and ecosystems could suffer as plants and animals struggle to adapt to erratic seasonal changes. For residents and visitors, the loss of a distinct autumn season could diminish cultural experiences like momijigari (autumn leaf viewing), a cherished tradition in Japan. Moreover, the lack of clear, sunny autumn days—often replaced by muggy, overcast weather—could affect mental well-being and tourism, both of which rely on the season’s picturesque charm.
Climate Change: A Global Perspective
Japan’s experience is not unique. Around the world, climate change is reshaping seasons, with hotter summers extending into what should be cooler months. In Europe, for instance, Mediterranean countries have reported similar trends, with autumns becoming shorter and winters arriving later. These changes underscore the urgent need for global action to mitigate climate change, from reducing carbon emissions to investing in sustainable practices. For travelers and locals alike, staying informed about local weather patterns and preparing for unpredictable conditions is becoming essential.
Adapting to a Changing Climate
As autumn continues to shrink, individuals and communities in Japan and beyond can take steps to adapt. For travelers planning to visit Japan in late 2025, packing lightweight, breathable clothing and staying hydrated will be key to enjoying the season despite the heat. Locals can explore indoor activities, such as visiting museums or attending cultural festivals, to make the most of the season. Meanwhile, supporting policies and initiatives aimed at combating climate change—such as renewable energy adoption or reforestation efforts—can help slow these alarming trends.
FAQs About Japan’s Changing Seasons
1. Why is September 2025 so hot in Japan?
The persistent heat in September 2025 is due to lingering high-pressure systems and elevated sea surface temperatures, both exacerbated by climate change. These factors trap warm, humid air over Japan, delaying the arrival of cooler autumn weather.
2. How is climate change affecting Japan’s autumn foliage?
Warmer temperatures are delaying the onset of autumn colors, particularly in regions like Hokkaido. When cooler weather arrives, it may do so abruptly, causing leaves to fall before they can fully change color, reducing the vibrancy of the foliage season.
3. What can travelers do to prepare for Japan’s extended summer heat?
Travelers should pack lightweight clothing, stay hydrated, and plan for indoor activities during the hottest parts of the day. Checking local weather forecasts and avoiding outdoor exertion during peak heat hours is also advisable.
4. How can individuals help combat the effects of climate change in Japan?
Supporting sustainable practices, such as reducing energy consumption, using public transportation, and advocating for policies that address climate change, can make a difference. Participating in local environmental initiatives, like tree-planting campaigns, is another impactful step.
Conclusion
Japan’s record-breaking heat in September 2025 serves as a stark reminder of climate change’s far-reaching effects. As autumn becomes shorter and less predictable, the cultural and natural beauty of the season is at risk. By understanding these changes and taking proactive steps—both individually and collectively—we can work toward a more sustainable future while still appreciating the fleeting charm of Japan’s autumn. Whether you’re a local or a visitor, staying informed and adaptable will ensure you can make the most of this evolving season.
