Check these websites daily for heatstroke warnings in Tokyo

The heat stress index is updated hourly, with information available in English

Tabea Greuner
Written by
Tabea Greuner
Tokyo landscape summer sun
Photo: Arto Marttinen/Unsplash

For a few days now, Tokyo has been hit by a heatwave, with daily temperatures exceeding 30 degrees Celsius. To help you avoid heatstroke, NHK World Japan provides this English website with information on the most recent heat stress index, also known as the Wet Bulb Globe Temperature (WBGT) index.

It calculates the temperature as well as the humidity and radiation levels, and assess their negative impact on our human body’s heat balance. Thanks to the easy-to-understand graph, you can see the index at different times of the day, so you know when to stay in and when it’s okay to go out. There’s also a forecast for the next day to help you plan accordingly.

To find out if a heatstroke warning has been issued for your area, you can also check this website by the Ministry of Environment, which is updated hourly.

Japan heat stress index
Photo: Ministry of Environment – screenshot of the heat stress index

As seen in the image above, the heat stress index indicates the heatstroke alerts that have been issued and in which region. There are also recommendations on the kinds of activities that should be avoided at certain WBGT levels.

While Japan is known for its extremely hot and humid summer, the effects of climate change have brought forth a massive heatwave. On Sunday July 7, Shizuoka city hit an alarming 40 degrees Celsius while large swathe of the country recorded crippling heat exceeding 35 degrees Celsius, including Tokyo. To put it into perspective, any temperature above 35 degrees Celsius is considered extreme heat in Japan.

So make sure to stay hydrated and avoid going out between noon and early evening when the temperature is at its peak. In case you feel ill or see someone who may be suffering from heatstroke, check this website on how to act accordingly.

This article was originally published in June 29 2022 and updated on July 8 2024.

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