Thread: Japan to start this year's Special Heat Stroke Alert system on Wednesday

Japan is set to begin this year's operation of its Special Heat Stroke Alert system on Wednesday in an effort to reduce health damage from extreme summer heat.

The Environment Ministry will issue a special alert when unprecedented levels of dangerous heat are expected.


Operation of the ordinary Heat Stroke Alert system for instances of possible heat-linked health risks will also begin the same day, and both systems will run through October 22.


When a heat stress index that factors in temperature and humidity, called the wet-bulb globe temperature index, is forecast to exceed the threshold of 35 at all observation points in a prefecture, the ministry will issue the special alert around 2 p.m. the day before.

While the special alert is in effect, municipalities will make air-conditioned facilities designated as cooling shelters open to the public.


Organisers of school events and other activities will be asked to consider cancelling or postponing them.


The ordinary alert system, operated by the Environment Ministry and the Japan Meteorological Agency, divides the country into 58 districts.


The alert will be issued around 5 pm the previous day or around 5 am that day if the heat stress index is forecast to stand at or above 33 at one or more observation points in a district.


The Special Heat Stroke Alert system was established in 2024.


The special alert has never been issued, while the ordinary alert was announced a record 1,722 times last year.


This may be due to the special alert requirement that all prefectural observation points be projected to show a high heat stress index, as the index tends to be lower at points of high altitudes.


"The special alert is information to prepare for when temperatures may exceed 40 degrees Celsius," a ministry official said.


"We hope people will take caution following ordinary alerts, which means it will be significantly hot."

Japan to start this year'''s Special Heat Stroke Alert system on Wednesday

Wet Bulb Calculator

^^The Japanese, too, are surprised when the temperature goes up to 40. A rare occurrence. I have to say, even 20 years ago we had to run air conditioners in the hot summer night to sleep.