Heatstroke Emergency Transports to Increase Approximately 2.1 Times After Rainy Season Ends in 2025; "Zero Heatstroke" Project Releases 2026 "Heat Acclimation Frontline" (2nd Edition)

The "Zero Heatstroke" project (hereinafter referred to as "the Project"), promoted by the Japan Meteorological Association (Headquarters: Toshima-ku, Tokyo; President: Kazuo Watanabe; hereinafter referred to as "JMA"), aims to widely raise awareness about the importance of "heat acclimation," which is preparing the body for heat before the full onset of summer. To this end, the 2026 "Zero Heatstroke Heat Acclimation Frontline (2nd Edition)" will be released on June 11, 2026 (Thursday) on the Project's official website (https://www.netsuzero.jp/le15-zensen). This frontline indicates the timing when heat acclimation becomes necessary in each region. Since the effects of heat acclimation diminish after a few days away from heat, information is repeatedly released at times when heat acclimation is needed in different areas. This 2026 "Heat Acclimation Frontline" will be the final report.

*1 What is Heat Acclimation?

One of the heatstroke prevention measures that can be taken before it gets hot is building a body that is resistant to heat. To build such a body, in addition to a balanced diet and sufficient sleep, "heat acclimation" is also important. Heat acclimation is the process of getting your body used to the heat. If you are not heat-acclimated, your body cannot effectively release heat, increasing the risk of heatstroke. While there are individual differences, heat acclimation typically takes from several days to about two weeks. Let's get our bodies used to the heat well in advance before the hot season begins.

About Heat Acclimation (Details): https://www.netsuzero.jp/learning/le15

■ What is the "Zero Heatstroke Heat Acclimation Frontline"?

The "Zero Heatstroke Heat Acclimation Frontline" indicates the timing to start "heat acclimation," which involves consciously sweating through light exercise or bathing to get the body accustomed to the heat.

■ Beware of the Intense Summer Heat After the Rainy Season Ends

It is particularly important to be cautious about heatstroke during periods like sunny spells during the rainy season or immediately after the rainy season ends, when the body is not yet accustomed to the heat. Furthermore, even if you have achieved heat acclimation, its effects will fade after a few days away from heat. If the temperature drops due to rain during the rainy season, the heat-acclimated body may revert to its previous state. Therefore, it is important to continue heat acclimation exercises and activities within a reasonable range.

In 2025, the number of emergency transports due to heatstroke increased approximately 2.1 times during the period before and after the end of the rainy season (Reference Material). In 2026 as well, the heat is expected to be severe after the rainy season ends, requiring vigilance against the heat.

[Zero Heatstroke: Preparing for the Heat] https://www.netsuzero.jp/learning/le20

■ Daily Life Activities for Heat Acclimation

Along with the timing to start heat acclimation, the Project will continuously share specific methods for heat acclimation on its official website and official X (formerly Twitter) account (@netsuzero2013).

■ Weather Trends Ahead

By Tomoko Kubo, Weather Forecaster / Disaster Prevention Specialist / Heatstroke Prevention Instructor, Japan Meteorological Association

From June to August, the jet stream is expected to flow slightly north of its average position over Japan, and the Pacific high-pressure system is likely to extend strongly towards Honshu. This will likely result in Japan being covered by warm air. Temperatures nationwide are expected to be higher than average, with another hot summer anticipated. It is advisable to engage in moderate exercise from an early stage, maintain a balanced diet, and get enough sleep to build a body that can withstand the heat. Especially after the rainy season ends, extremely intense heat comparable to last year is expected, with some areas in Eastern and Western Japan potentially experiencing record-high temperatures exceeding 40°C. It is crucial to take breaks, stay hydrated by drinking water before feeling thirsty, and implement thorough heatstroke prevention measures. The El Niño phenomenon is expected to continue into autumn, and Western Japan may experience the effects of typhoons and frontal systems in the latter half of summer. High humidity and muggy days are likely, so it is important to maintain a comfortable indoor environment and adapt clothing to prevent heat buildup in the body.

Reference Material: Review of Summer 2025

The rainy season ended around June 7-9 for Okinawa and Amami, June 27-29 for Kyushu, Shikoku, Chugoku, Kinki, Tokai, Kanto-Koshin, and Hokuriku, and around July 18 for Tohoku in 2025. According to the Fire and Disaster Management Agency, comparing the week before the rainy season ended (June 23-29) with the week after (June 30-July 6), the number of heatstroke emergency transports increased from 4,772 to 10,187, an approximately 2.1-fold rise. Furthermore, the week of July 22-28, after the rainy season ended in Tohoku, saw continued severe heat nationwide, with 10,997 emergency transports, marking the highest weekly total for 2025.

■ Changes in Emergency Transports Before and After Rainy Season End

■ About the "Zero Heatstroke" Project

The "Zero Heatstroke" project, promoted by the Japan Meteorological Association, aims to reduce the number of people suffering from heatstroke and eliminate fatalities. Since its launch in the summer of 2013, the project has focused on disseminating weather information that significantly influences heatstroke occurrences, thereby raising awareness about correct knowledge and countermeasures against heatstroke. In 2026, its 14th year, the project's theme is "Supporting Those Responsible for Heatstroke Prevention," focusing on practical awareness activities. With the increasing severity of heat in recent years, the importance of supporting personnel involved in heatstroke prevention has grown, highlighted by the mandatory implementation of heatstroke countermeasures for companies starting in June 2025. The project aims to enhance disaster preparedness awareness throughout society by providing information that supports awareness campaigns for those overseeing organizations and communities.

■ About the Japan Meteorological Association

The Japan Meteorological Association was established in 1950 as a pioneer in private meteorological consulting. Beyond disaster prevention, mitigation, and offshore wind power generation, the association continues to propose the business utilization of meteorological data through consulting services in areas such as product demand forecasting, electricity demand forecasting, and climate change countermeasures. With over 370 affiliated weather forecasters, it stands as one of Japan's largest groups of meteorological experts, actively supporting companies' ESG investments and SDGs initiatives.

- "Zero Heatstroke" is a registered trademark of the Japan Meteorological Association.