Last June's Heatstroke Transport Numbers Hit Record High, Yet 35% Start Heatstroke Measures in July or Later: Expert Explains 'Rainy Season Heatstroke' to Watch Out For Now

According to the Japan Meteorological Agency's summer weather outlook, temperatures from June to August this year are expected to be high nationwide due to warm air masses, with a risk of continued 'extreme heat'. The average summer temperature in 2025 significantly exceeded previous records, becoming the highest since statistics began, and severe heat is also forecast for this year.

Furthermore, according to statistics from the Fire and Disaster Management Agency, the cumulative number of emergency heatstroke transport patients from May to September 2025 was 100,510, an increase of 2,932 from 2024. Due to the record-breaking heat, this exceeded 100,000 for the first time since the survey began in 2008, marking an all-time high. Notably, the number of emergency transport patients in June, when the monthly average temperature was the highest on record, was 17,229, also a record for a single month. Heatstroke countermeasures remain crucial this summer as extreme heat is forecast.

On the other hand, rising prices for various daily necessities and electricity bills are directly impacting household budgets, raising concerns about 'air conditioner restraint' due to electricity costs.

In light of this, Panasonic Corporation conducted a survey on summer air conditioner use and heatstroke. Additionally, Panasonic Air Master and Heatstroke Prevention Instructor Fukuko Fukuda will introduce heatstroke countermeasures that are mindful of energy saving.

[Press Release Summary]

■ Survey on Heatstroke Conducted

・ 78% 'usually take heatstroke measures'
・ 35% start heatstroke measures 'in July or later'
・ 82% 'do not know the details' or 'have never heard of' rainy season heatstroke
・ 43% 'do not consciously take measures against indoor humidity from the perspective of heatstroke prevention'
・ 32% 'do not have a habit of sweating'

■ Beware of Rainy Season Heatstroke! Expert Doctor's Guide to Countermeasures

Explained by Dr. Tsuyoshi Fujinaga, Vice Director of Saitama Jikei Hospital

■ Panasonic Air Master and Heatstroke Prevention Instructor Explains Summer Air Conditioner Energy-Saving Tips

Heatstroke countermeasures through proper air conditioner cooling use

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82% 'Do Not Know Details' or 'Have Never Heard of' Rainy Season Heatstroke

While 78% 'Usually Take Heatstroke Measures', 35% Start in 'July or Later'

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First, regarding usual heatstroke measures, 78% of respondents indicated they take some form of action, with 32% saying they 'actively take measures' and 46% saying they 'somewhat take measures'.

Regarding the timing for starting heatstroke measures, 35% begin in July or later, with 29% starting in 'July' and 6% in 'August'. However, the rainy season is a time when 'rainy season heatstroke' is likely to occur, where heatstroke risk increases due to humidity even if temperatures are not very high, making countermeasures before the peak of summer important.

Next, regarding awareness of 'rainy season heatstroke', only 18% said they 'know both the term and its content', while 23% said they 'have heard the term but do not know the details' and 59% said they 'have never heard of it', revealing that 82% are not familiar with it.

Regarding awareness of indoor humidity as a heatstroke countermeasure during the rainy season, 57% said they are conscious of it, with 19% saying 'very conscious' and 38% saying 'somewhat conscious'. On the other hand, 43% are not conscious of humidity, with 32% saying 'not very conscious' and 11% saying 'not conscious at all'.

Another important heatstroke countermeasure is 'heat acclimatization', which involves getting the body used to heat and high humidity. As detailed later, it is important to develop a habit of sweating through exercise or bathing. Regarding the habit of sweating, 68% have a habit, with 34% saying 'almost every day' and 34% saying 'several times a week', while 32% do not have a sufficient habit of sweating, with 24% saying 'not very often' and 8% saying 'not at all'.

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Caused by High Humidity!? Beware of Heatstroke Before Summer

Expert Doctor's Guide to 'Rainy Season Heatstroke' Countermeasures

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We asked Dr. Tsuyoshi Fujinaga, Vice Director of Saitama Jikei Hospital and an expert on heatstroke, about the mechanism and countermeasures for 'rainy season heatstroke'.

*Quoted and published from the Panasonic website 'UP LIFE'.

What is 'Rainy Season Heatstroke' to Watch Out for Before Summer?

Rainy season heatstroke is a type of heatstroke that tends to occur during the rainy season before the peak of summer. It can occur even if the temperature is not as high as midsummer, especially if humidity is high, and is more likely to develop on days with weak wind. A characteristic is that it often occurs indoors.

What is the Mechanism of Rainy Season Heatstroke?

When humidity is high, sweat does not evaporate easily, causing heat to build up in the body and raising body temperature. The body then sweats to try to lower its temperature, leading to dehydration. Additionally, high humidity makes it difficult to feel thirsty, so fluid intake is neglected, further advancing dehydration. Repeating this process gradually weakens the body's temperature regulation function, making it unable to lower body temperature. Heatstroke is thus caused by a combination of 'rising body temperature' and 'dehydration'.

What are the Countermeasures for Rainy Season Heatstroke?

Prevention of rainy season heatstroke includes: 1) appropriate temperature and humidity (guideline: room temperature 25-28°C, humidity 50-60%), 2) frequent fluid intake, and 3) acquiring heat acclimatization. For 1), adjust by ventilating, circulating air with fans or circulators, and using the dehumidification function of air conditioners. It is important to lower not only temperature but also humidity. For 2), the trick is to drink before you feel thirsty. For 3), heat acclimatization means getting used to heat and high humidity. Once heat acclimatization is complete, the amount of sweat increases, helping to prevent a rise in body temperature.

While many people are now aware of heatstroke in midsummer, rainy season heatstroke is still not well known. It is more important to first understand it than to fear its onset.

For more details on dealing with rainy season heatstroke, please see here:

https://panasonic.jp/life/health/160095.html

Tsuyoshi Fujinaga

Doctor, Ph.D. in Medicine. Vice Director of Saitama Jikei Hospital. After graduating from The Jikei University School of Medicine, he worked at the university hospital and Toranomon Hospital before joining Saitama Jikei Hospital in Kumagaya City, Saitama Prefecture in 1996. He has been engaged in emergency heatstroke medical care for about 30 years, treating many patients. Due to the region's high number of heatstroke patients, heatstroke treatment has become his life's work. Even as Vice Director, he continues to be on the front lines treating heatstroke patients brought in by emergency services. He has made numerous appearances on domestic and international media, including NHK, commercial broadcasters, and CNN.