Japan’s Weather in 2026: Prepare for Extreme Heat, Increased Rain, and Typhoons — Long-Term Forecast by Japan Weather Association

2026.02.06

According to the long-term weather forecast by Japan Weather Association, 2026 is expected to be a year characterized by an early onset of summer, extreme heat, and increased rainfall.

This article explains the key weather characteristics of 2026, seasonal highlights, potential business impacts, and how to effectively utilize long-term weather forecasts.

For the reference: Japan’s 2025 Weather Review — Business Impacts of a Cold Winter and Record-Breaking Heat

Highlights of Japan’s 2026 Weather Outlook

• Spring 2026: Large temperature fluctuations are expected, although the onset of heat is likely to be early.
• Summer 2026: Both the start and end of the rainy season are expected to occur earlier than usual, with extreme heat and a tendency toward higher-than-2025 rainfall.
• Late Summer to Fall 2026: Lingering summer heat is expected, along with increased risks of prolonged rainfall and typhoons.

＊For characteristics of Japanese weather: Why Is Japan’s Weather So Difficult to Forecast? ―How the Four Seasons and Topography Create Weather Complexity and Affect Businesses―

Table of Contents

Weather Outlook for 2026

Key Characteristics of 2026 Weather

• The start and end of the rainy season will be early, leading to an early onset of summer.
• Extreme heat is expected, but rainfall will be higher than in 2025.
• From late summer to fall, caution is needed for prolonged rainfall and typhoons.

These conditions are expected because the La Niña–like tendency that persisted through 2025 is gradually weakening. As a result, it is less likely for the Pacific High to strengthen from the latter half of summer, which is expected to make Japan more susceptible to the influence of weather fronts and typhoons.

Winter 2025/26 Forecast: Two Consecutive Years of Cold Winter Trend

The winter of 2025/26 is expected to continue a cold winter trend for the second consecutive year, influenced by sea surface temperature patterns similar to La Niña conditions. Although cold conditions will persist throughout the season, they are expected to ease slightly from February onward, potentially bringing an earlier onset of spring compared with 2025.

Spring 2026 Forecast: Large Temperature Swings and Early Warming

Spring 2026 is expected to experience significant temperature fluctuations, with an overall early warming trend. Pollen dispersal is forecast to be higher than the previous season, particularly in northern and eastern Japan, which may advance demand for spring clothing, outdoor activities, and allergy-related products.

Summer 2026 Forecast: Intense Heat with Increased Rainfall

In summer 2026, the Pacific -High pressure system is expected to strengthen earlier, resulting in an earlier-than-usual start and end of the rainy season.
The onset of heat will also be early, and there is a possibility of extreme heat conditions.

However, the Pacific High is unlikely to persist, making this summer characterized by high temperatures and increased precipitation, unlike the summer of 2025, which was characterized by markedly low rainfall.

From a business perspective, attention should be paid to the following potential impacts:

• Increased risk of heatstroke
• Earlier peak in electricity demand
• Changes in demand due to extreme heat, including reduced outdoor activity and cancellation of sports events
• Localized heavy rainfall caused by autumn rain fronts and typhoons

Fall 2026 Forecast: Unstable Weather Conditions Due to Typhoons and Prolonged Rainfall

From late summer into autumn 2026, the dissipation of La Niña–like tendency is expected to make Japan more susceptible to the influence of weather fronts and typhoons. As in 2025, severe lingering heat is likely to continue, but unlike 2025, rainfall is expected to increase due to prolonged rainy periods and approaching typhoons, potentially raising business risks associated with unstable weather conditions.

How Will 2026 Differ from 2025? Key Weather Points to Note

In 2025, the year was characterized by the following features:

• Winter was marked by strong cold air moving southward.
• Summer saw pronounced extreme heat and notably low rainfall.

In contrast, 2026 will differ in the following key ways:

• Strong cold air moving southward during winter, similar to 2025.
• Summer is expected to be extremely hot, with a tendency toward higher-than-normal rainfall.

From the latter half of summer onward, businesses are likely to need measures to mitigate rainfall-related risks.

Why Will 2026 Experience These Weather Patterns?

The weather in 2026 will be influenced primarily by the following factors.

The Weakening of La Niña–like tendency and the Pacific High

• Winter to spring: Continued influence of La Niña–like tendency
• Early summer: Residual La Niña–like tendency effects will strengthen the Pacific High earlier, leading to an earlier start and end of the rainy season.
• Late summer to fall: As the residual effects of La Niña–like tendency fade, the Pacific High is less likely to strengthen, making Japan more vulnerable to weather fronts and typhoons.

El Niño / La Niña Phenomena and Japan’s Weather

Seasonal characteristics such as warm winters or cool summers are typically influenced by variations in sea surface temperatures across the tropical Pacific Ocean—notably the El Niño*1 and the La Niña*2 phenomena.

When sea surface temperatures in the tropical Pacific deviate from normal patterns— during El Niño or La Niña events—cumulonimbus clouds tend to develop in atypical regions, and the mid-latitude westerlies are more likely to follow unusual paths.

As a result, regions far from the tropics, including Asia (Japan included) and North America, are more likely to experience weather conditions that differ from normal.

*1 El Niño phenomenon: A climate event in which sea surface temperatures from near the International Date Line in the central equatorial Pacific to the coast of South America become higher than normal, with conditions persisting for about one year. In Japan, El Niño tends to bring cooler summers and warmer winters.

*2 La Niña phenomenon: A climate event in which sea surface temperatures from near the International Date Line in the central equatorial Pacific to the coast of South America become lower than normal, and the condition continues for about one year. In Japan, La Niña tends to bring hotter summers and colder winters.

Impacts of 2026 Weather on Businesses

Impact on the Apparel Industry

• Demand for spring and summer products is expected to rise earlier than usual.
• Severe lingering summer heat is likely to delay the start of fall apparel demand; however, the arrival of winter is also expected to be late, potentially extending the overall demand period for fall items compared with 2025.

By understanding long-term temperature trends and seasonal patterns in advance, companies can reduce inventory losses and missed sales opportunities.

Impact on the Energy Industry

• Increased demand for heating during winter.
• Earlier and more prolonged peak demand for summer cooling.
• Potential instability in solar power generation due to prolonged autumn rainfall and typhoons.

Utilizing medium- to long-term weather forecasts is essential for supply–demand planning and risk management.

Impact on the Manufacturing Industry

• Early rise in demand for summer-related products such as cooling goods and beverages.
• The need to monitor changes in demand patterns driven by heat-related lifestyle changes.
• Increased production and logistics risks associated with typhoons and prolonged rainfall.

Impact on the Retail Industry

• Need to accelerate in-store roll-out of summer-related merchandise.
• Large temperature fluctuations make inventory adjustments based on short-term forecasts increasingly important.

Impact on the Logistics Industry

• Prolonged rainfall and typhoons from late summer through fall may cause delivery delays and inventory imbalances.
• Need to respond to fluctuations in logistics volumes caused by temperature variability.
• Increased importance of measures to improve working conditions, particularly heat-related countermeasures.

Impact on Agriculture

• The early onset of extreme heat may affect crop growth and yields.
• Unstable weather from late summer through fall may pose risks to crop quality and production volumes

How to Make Use of Long-Term Weather Forecasts

Seasonal trends vary significantly from year to year, including record-breaking heat and cold winters following warm winters. As a result, it has become increasingly difficult to optimize resource procurement, production, inventory, and energy supply–demand planning using only short-term weather forecasts and meteorological information.

By developing annual plans based on long-term weather forecasts and making adjustments using short-term forecasts, companies can comprehensively reduce disposal losses and missed business opportunities caused by weather-related factors.

What Is Japan Weather Association’s “2-Year Long-Term Weather Forecast”?

Japan Weather Association provides the “2-Year Long-Term Weather Forecast,” the first forecasting service in the meteorological industry to offer weather predictions up to two years in advance.

Insights Available Through the 2-Year Long-Term Weather Forecast

• Monthly numerical forecasts of temperature, amounts of precipitation and snowfall, and sunshine duration
• Region-specific forecasts for the start and end of the rainy season
• Monthly forecasts of the number of typhoons formed and those approaching Japan

＊Note: Available content varies depending on the service contract. Please contact us for details.

Industries and Use Cases for the 2-Year Long-Term Weather Forecast

Since its launch in June 2024, Japan Weather Association’s “2-Year Long-Term Weather Forecast” has been widely used by companies across various industries for demand forecasting, material procurement, product planning, production adjustment, and marketing planning.

In particular, apparel companies, manufacturers of household goods, and food industry—where lead times from product planning to sales are long—are increasingly using the forecast across a wide range of stages, from product planning to production adjustment.

There has also been strong feedback from the electric power and energy sectors, with many users reporting that the service is helping to improve long-term power demand forecasting and optimization of fuel procurement.

One of the user companies has reported that “power demand forecasting accuracy improved by 30%.”

＊For more details: Accuracy and Use Cases of the “2-Year Long-Term Weather Forecast” (Only Available in Japanese)

For detailed, region- or month-specific information on weather conditions in 2026, contact us.

We can also provide proposals on weather trends from the latter half of 2026 through 2027, based on the latest available data.

Contact us for a consultation to incorporate long-term weather risks into management and planning in advance.

For details on 2-Year Long-Term Weather Forecasts, please see:

• 2-Year Long-Term Weather Forecast (Only Available in Japanese)
• What are Long-Term Forecasts? JWA’s Proprietary “2-Year Long-Term Weather Forecast” and Its Business Applications Part 1 / Part 2

For snow conditions outlook of this winter, please see:

＊Outlook for Snow Conditions at Japan’s Ski Resorts in Winter 2025/26: Snowfall Amounts Are Expected to Be Near or Above Average in January and February, and Near or Below Average in March

Product rankings that sell well in cold weather, please see:

＊Top 10 Food Products / Top 5 Daily Necessities
Winter 2025–26 Expected to Bring “Seasonal Cold” — Latest Winter Forecast and Rankings of “Cold-Weather Best-Selling Products” [Japan Weather Association Weather X Analysis] (Only Available in Japanese)

Frequently Asked Questions

Q. How much detail can be forecast up to two years ahead?

A. We can provide numerical forecast data for monthly temperature, amounts of precipitation and snowfall, and sunshine duration.

Q. Is the information updated regularly?

A. The forecasts are updated monthly based on the latest available data.

Q. Can the analysis be made by region?

A. Yes. We also offer trend analysis by region.

Professional Profile

Kumi Okoshi

The weather analysis and discussion of business impacts presented in this article have been supervised by Kumi Okoshi, Senior Data Analyst at Japan Weather Association.

In her role within JWA’s product demand forecasting business, she conducts market-oriented analyses and demand forecasts for industries such as food, daily necessities, and apparel, and provides consulting services to help companies address a wide range of business challenges.