Japan, a country where the seasons change—The record early end of the rainy season in Western Japan indicates the future

Japan, a country where the seasons change—The record early end of the rainy season in Western Japan indicates the future

2025年06月27日 19:45

1. The Shortest Rainy Season on Record—What Happened?

In Western Japan, the rainy season front, which typically lasts until mid-July, dissipated by June 27 without moving north or stagnating. The reasons include an unusual extension of the Pacific high-pressure system and the meandering of the westerlies. An official from the Meteorological Agency stated that "the strong high pressure is not expected to weaken soon," acknowledging long-term changes without directly attributing them to climate change.phys.org


1-1 The "June Peak" of the Pacific High-Pressure System

Satellite observations of water vapor and sea surface temperature (SST) analysis show that the heat accumulated by the Kuroshio's large meander strengthened the high pressure. The latent heat supply from the sea pushed the front northward, quickly depleting the rainy season front's energy.


1-2 Earlier "Rainy Season Start"

In mid-May, Southern Kyushu entered the rainy season 14 days earlier than usual, becoming the "fastest starter" for the first time since records began, excluding Okinawa and Amami.nippon.com This combination of "earlier start + early end" indicates a trend of "compression" of the rainy season itself.



2. The Shifting of Four Seasons—Risk of Spring and Autumn Disappearing

Climate experts point out that "seasons are defined not by sentiment but by temperature, precipitation, and ecosystems." A feature by Nippon.com warned of the danger of transitioning to a "two-season system" as the durations of spring and autumn shorten.nippon.com


  • Shortening of Spring: The blooming of cherry blossoms has advanced by an average of 5 days since the 1980s, with mid-March blooming becoming the norm in Tokyo.

  • Shortening of Autumn: The southward movement of the autumn foliage front is delayed by 1 to 2 weeks.

  • Impact on Ecosystems: Cedar pollen dispersal starts earlier due to high temperatures, and the occurrence of high-temperature damage to rice, known as "white immature grains," is increasing.



3. The Scientific Background of Climate Change

The Ministry of Education, Culture, Sports, Science and Technology and the Meteorological Agency's "Climate Change IN Japan 2025," published in March 2025, compares 2°C and 4°C scenarios, predicting that the occurrence of heavy rain exceeding 50 mm/h will increase by 1.8 to 3 times.50 mm/h以上の豪雨発生回数が1.8～3倍に増えると予測する。data.jma.go.jp The simultaneous progression of "shorter but more intense rainy seasons" is highly likely.


3-1 Changes in Atmospheric Circulation

With Arctic warming, the temperature difference between the poles and the equator decreases, causing the westerlies to meander → blocking high-pressure systems stagnate for long periods → frequent delays and shortening of the rainy season.


3-2 The Role of the Ocean

Changes in the routes of the Kuroshio and Oyashio currents alter heat and water vapor transport, with rising SSTs near Japan leading to early rainy season ends and heatwaves in midsummer.



4. Impact on Life and Industry

FieldExample of ImpactDescription
AgricultureShift to Early Planting and HarvestingThe heading period of rice coincides with high temperatures, leading to quality deterioration. Urgent shift to high-temperature resistant varieties is needed.
Tourism"Rainy Season-less" Inbound Tourism and Heatstroke RiskIncreased sunny days in June boost foreign tourism, but heatwave countermeasures are a challenge.
InfrastructureAlternating Floods and DroughtsShort-term heavy rains cause river flooding → immediate drought, necessitating flexible dam operations.
CultureReorganization of Seasonal EventsThe climate presentation of events like Tanabata and Gion Matsuri changes, requiring adjustments in seasonal marketing strategies.



5. Foreigners' Perception of "Changing Seasons"

Visitors to Japan look forward to experiencing its four seasons. In the first half of 2025, inbound tourism surpassed 3 million per month, and **"comfortable even during the rainy season"** could become a new catchphrase. However, if spring and autumn shorten, the concentration of tours for cherry blossoms and autumn leaves may increase, worsening overtourism concerns.



6. What We Can Do—Mitigation and Adaptation

  1. Mitigation: Expanding the share of renewable energy and creating carbon-neutral urban areas.

  2. Adaptation: ① High-temperature resistant crops, ② Urban green infrastructure, ③ Diversification of tourism.

  3. Information Dissemination: Governments and municipalities should provide real-time updates on "seasonal changes" in multiple languages to enhance the safety of travel planning.


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