The Environment Ministry is starting to upload heat indices and forecasts for 841 locations to its website, accompanied by a warning system to alert the public to the risk of heatstroke.
The heat index projections on the website (www.wbgt.env.go.jp/), include temperature, humidity and radiant heat, and indicate five danger levels — "risky," "strong caution," "caution," "attention" and "generally safe."
The warnings, in Japanese, are updated every hour. As for the forecasts, updates are provided on a map every three hours for the present day, the following day and the day after.
The ministry increased the number of monitoring spots to 841 from about 150 last year. It started displaying the data on May 13 and will update it until Oct. 18.
The Environment Ministry says that people should avoid staying outside when the risk is high. Heatstroke cases have been on the rise due in part to Japan's heat island phenomena and global warming.
It also says it is helpful to grow morning glories and bitter melons at buildings to make shade and cut internal temperatures.