Disaster Preparedness / Preventing Heatstroke During Power Outages, Knowing the Signs

Yomiuri Shimbun

20-07-2025

When the power goes out during a typhoon or if there is a power outage in the summer, air conditioners will not work, increasing the risk of heatstroke. Power outages can last for a long time, and it is necessary to know how to keep cool without relying on electrical appliances. You should also keep in mind what to do if you suspect heatstroke.
***According to the Japan Meteorological Agency's three-month forecast, the average nationwide temperature from June through August is expected to be higher than usual. 'In recent years, the summer heat has been extremely severe, and it is essential to take measures to prevent heatstroke on a regular basis,' said preparation and disaster prevention advisor Tomoya Takani. 'Consider preparations with goods that you usually use to prevent heatstroke.'
Such items include portable fans that come with a battery and can be used even during power outages. However, fans will blow hot air in a room without air conditioning, which may increase the risk of heatstroke. If you wet your T-shirt with water, you can use the evaporation to cool your body.
Power banks that are used to charge smartphones can also charge portable fans. If the power bank uses AA or AAA batteries, you can use the batteries from a TV remote or other device.
In addition, you should also prepare neck coolers and sprays containing cooling ingredients like menthol.
Make sure your room is well ventilated. Open at least two windows or doors to improve ventilation. It is important to open windows and doors on opposite sides of the room. Shades and drapes on windows can help prevent heat from direct sunlight.
Clothing should be made of breathable and quick-drying materials such as polyester. 'Prepare for disaster while making good use of convenient tools,' said Takani.
Measuring danger level
'If you are not used to the heat, you are more likely to suffer heatstroke,' said emergency physician Yasufumi Miyake, director of the Organization on Development and Progress for Education in Clinical Medicine. 'If the air conditioning is suddenly disabled in a disaster, the risk increases dramatically.'
The risk level of heatstroke can be determined by the Wet Bulb Globe Temperature (WBGT), which is the index calculated from data such as temperature, humidity and solar radiation. According to the guidelines of the Japanese Society of Biometeorology, the WBGT index indicates a 'Severe Warning' for heatstroke between 28 C and 31 C, and when the index is 31 C or higher, the warning rises to 'Danger.'
Miyake recommends installing a heatstroke meter or other device that displays the WBGT index at home to assess the risk of heatstroke. The Japan Meteorological Agency issues a 'heatstroke alert' when the WBGT index is estimated to be 33 C or higher. 'On days when temperatures are expected to rise, consider evacuating to a shelter with an emergency power supply or to an air-conditioned car, and take action as soon as possible,' said Miyake.
You should also be aware of the symptoms of heatstroke. These include feeling dizzy, numbness in the arms and legs, a headache and nausea. If the person is barely conscious or unable to speak, call an ambulance as soon as possible.
If the person can speak, move them to a shady area, give them water and salt and cool their neck and armpits. If their symptoms do not improve, have the person seek medical attention. 'If you notice anything unusual, suspect heatstroke,' said Miyake.