Japan's government has begun its annual operation of its heat-related illness prevention alert system, which includes a new Special Heat Stroke Alert.
The Ministry of the Environment and the Japan Meteorological Agency initiated the system on Wednesday.
The Special Heat Stroke Alert will be issued for prefectures where the heat index, based on factors such as temperature and humidity, is predicted to hit 35 or higher at all observation points.
It is one level above the conventional Heat Stroke Alert, which is issued when the index is expected to reach 33 or higher.
The new alert is expected to indicate dangerously high temperatures that could pose significant health risks on an unprecedented scale across a wide area.
Japan has never experienced heat that would call for a Special Heat Stroke Alert.
Prefectures where the alert is issued will be required to take thorough actions to prevent heatstroke.
Local governments must designate public and private air-conditioned facilities as "cooling shelters" in advance, and open them when an alert is issued.
School principals, business managers and event organizers will also be required to take comprehensive measures against heatstroke.
If they are unable to sufficiently implement such measures, they must decide on actions such as canceling sports activities and events and switching to remote work.