What Was Japan’s Summer Like in 2026? Temperatures, Precipitation, Typhoons, and Key Points for Businesses

2026.10.26

Summer 2026 brought record-breaking heat and low precipitation, particularly in western Japan, while precipitation was significantly above average on the Pacific side of eastern Japan due to typhoons and events such as the August 2026 Chiba Heavy Rain. The number of typhoons that formed during the summer was also well above average.

Summer 2026 was characterized not simply by high temperatures, but by the varying impacts of high temperatures, low precipitation, localized heavy rainfall, and typhoons across region and period.

This article reviews three key characteristics of summer 2026 and explains the points businesses should consider when reviewing their own performance and considering future plans.

Table of Contents

Three Key Characteristics of Summer 2026

Summer 2026 was characterized by regional differences in the way heat and precipitation occurred, as well as by the number of typhoons that formed.

The three key points that characterized summer 2026 are outlined below.

*1 Total average number of typhoons forming during the summer months of June through August.

A Data-Based Review of Temperatures, Precipitation, and Typhoons in Summer 2026

Summer 2026 was not as hot nationwide as 2025, but it still brought extreme heat in some regions and a large number of typhoons.

A comparison of the main indicators with 2025 and the average is shown below.

*The number of typhoons approaching Japan refers to cases in which the center of a typhoon came within 300 km of any meteorological observatory or other designated observation point in Japan.

Japan’s average temperature in summer 2026 was 1.02°C above average, making it the fifth-highest summer temperature since records began in 1898.

Although the nationwide average was lower than the +2.36°C recorded in 2025, both the total number of occurrences of daily maximum temperatures of 40°C or higher and the number of typhoons that formed exceeded the 2025 figures.

In terms of precipitation, low precipitation was particularly notable in 2025 on the Pacific side of northern and eastern Japan.

In 2026, regions with high and low precipitation were more clearly divided. Precipitation was low in areas such as the Sea of Japan side of western Japan, while the Pacific side of eastern Japan and Okinawa and Amami experienced higher rainfall.

1. Record-Breaking Heat Particularly in Western Japan, with 36 Occurrences of Daily Maximum Temperatures of 40°C or Higher

Average summer temperatures in 2026 were 1.2°C above average in northern and western Japan and were assessed as “significantly above average.” In eastern Japan, temperatures were 0.8°C above average and were assessed as “above average.” In particular, western Japan experienced its third-hottest summer since records began in 1946.

The main records were as follows.

• Japan’s average temperature in summer 2026 was 1.02°C above average, the fifth highest since 1898.
• Western Japan experienced its third-hottest summer since 1946.
• Daily maximum temperatures of 40°C or higher were recorded at 22 locations, with 36 occurrences, the highest number since 2010.
• Although the nationwide degree of high temperatures was lower than in 2025, extreme heat occurred locally.

The main factors behind these high temperatures were that the westerly winds flowed farther north than average around Japan and that western Japan was covered by a well-developed high-pressure system extending from the upper atmosphere to the surface. Descending air currents, strong solar radiation, and an inflow of warm air occurred simultaneously. The high temperatures in western Japan were also analyzed as having been influenced by the underlying rise in temperatures associated with global warming.

* [Japan Meteorological Agency] On the Significant High Temperatures from Mid- to Late July 2026 and the Outlook Ahead

*For information on how the Pacific High, which is closely related to summer heat, works and how it relates to the rainy season and typhoons, see the related article, “What Is the Pacific High? How It Relates to Summer Heat, the Rainy Season, and Typhoons.”

2. Low Precipitation in Western Japan Alongside High Precipitation on the Pacific Side of Eastern Japan

Another characteristic of summer 2026 was the extremely large regional difference in precipitation.

Over the summer as a whole, precipitation was 133% of average on the Pacific side of eastern Japan and 148% in Okinawa and Amami, while it was 88% on the Sea of Japan side of eastern Japan and 83% on the Sea of Japan side of western Japan.

These regional differences reflected the varying influence of pressure patterns, fronts, and typhoons across different regions during the summer.

The low precipitation centered on western Japan was caused by frequent sunny weather under high-pressure systems and limited influence from low-pressure systems and fronts. In contrast, the Pacific side of eastern Japan was more susceptible to the effects of the Baiu front, typhoons, and moist air, and some areas experienced record-breaking heavy rainfall.

When reviewing such heavy rainfall events, one approach is to consider not only the absolute amount of rainfall but also how it compares with the highest amount of rainfall previously recorded in that region. This concept of the “ratio to the historical maximum” is explained in “What Is the ‘Ratio to the Historical Maximum’ for Rainfall? An Indicator for Earlier Assessment of Heavy Rain Disaster Risk and Its Use in Corporate BCP.”
Related article: Heavy Rain and Flooding Countermeasures for Facilities | Risks and Decision-Making Points for Factories, Warehouses, and Stores

3. Seventeen Typhoons Formed During the Summer, and Typhoon No. 15 Followed an Unusual Track

A total of 17 typhoons formed during summer 2026, far exceeding the average of 11.1 and tying for the third-highest number since records began in 1951.

One of the main factors behind the large number of typhoons was the increased activity of easterly waves during July and August. Easterly waves are wave-like atmospheric disturbances that move from east to west within tropical easterly winds and can sometimes trigger typhoon formation. In the first half of August, some typhoons also formed around a large-scale low-pressure system known as a “monsoon gyre” that developed over the ocean south of Japan.

Because easterly waves tend to become more active during summers when El Niño conditions are present, the pronounced El Niño event may have contributed to the large number of typhoons in summer 2026.

Summer 2026 was characterized not only by the large number of typhoons but also by their tracks. In particular, Typhoon No. 15 followed an unusual track with few historical precedents, moving from the ocean east of Japan, making landfall in Ibaraki Prefecture, and then traveling westward across Honshu.

This unusual track was influenced by a monsoon gyre, a large and broad low-pressure circulation that formed over the ocean south of Japan, as well as a strong high-pressure system over the ocean east of Japan. Analysis indicates that Typhoon No. 15 moved westward along the wind flow between these low- and high-pressure systems and was also affected by an upper-level cold low moving southward.

Related articles

• Japan’s 2026 Typhoon Outlook: Trends in Typhoon Formation and Approaches to Japan in September and October [Updated July 30]
• How Do Typhoons Affect Logistics? Operational Decisions, Delivery Delays, and Risks by Transportation Route
• What Are the Benefits of Viewing Multiple Typhoon Track Scenarios? How Businesses Can Use “Scenario-Based Typhoon Forecast Information”

Three Points Businesses Should Keep in Mind When Reviewing Summer 2026

When using the results from summer 2026 as a reference for the following year and beyond, it is important to review changes in sales, demand, production, inventory, equipment load, and other business indicators in relation to the weather conditions in the regions and periods that affected the company’s operations.

However, specific order volumes, production volumes, or operational standards cannot be determined from weather data alone.

Weather data should be used as one source of information for planning in combination with a company’s own performance data, market trends, and other information.

Reviewing the relationship between weather conditions and business performance in summer 2026 can provide useful information when considering future plans.

However, when developing actual plans or responding operationally, companies need to reconsider the type of weather information they use depending on the timing of the decision.

Connecting the Review of Summer 2026 to Future Use of Weather Information

When companies use weather information for planning and operations, it is important to check long-term trends at an early stage and then gradually shift to forecasts focused on more specific regions and time periods as implementation approaches.

For more information on how to avoid simply using 2026 results as the assumptions for the following year’s plan and instead combine previous-year results with future weather forecasts, see “How Can 2-Year Long-Term Weather Forecasts Be Used for Business Planning? Applications to Decision-Making for the Next and Following Fiscal Years.”

For details on monthly and regional forecasts and analyses that combine weather information with your company’s own data, see the service details for 2-Year Long-Term Weather Forecasts.

The information available and situations in which it can be used vary depending on the forecast period. “How Should Weather Data Be Used Differently? Differences Between Short-, Medium-, Long-, and Extended-Long-Range Forecasts and Their Business Applications” provides a detailed explanation of the characteristics of each forecast period.

Summary | Summer 2026 Was Characterized by Significant Differences by Region and Period

• Summer 2026 was characterized by high temperatures and low precipitation particularly in western Japan, high precipitation on the Pacific side of eastern Japan, and an above-average number of typhoons.
• Businesses need to review conditions not only on the basis of nationwide averages but also by the regions and periods that affected their own locations and operations.
• Rather than using 2026 results directly as the basis for planning the following year, it is important to combine them with average conditions, results from multiple years, and future weather forecasts when developing future plans.

The significant variation in weather conditions across regions highlights the need for location-specific analysis when reviewing business performance and planning future operations.

When businesses review summer 2026, it is important to examine not only nationwide averages but also weather data corresponding to their own locations and market areas together with business performance. It is also necessary to avoid using weather conditions specific to 2026 directly as assumptions for the following year and instead consider long-term outlooks together with the latest forecasts.

FAQ | Frequently Asked Questions