TOKYO, Aug. 17 (Xinhua) -- Japan on Thursday issued the highest-level heatstroke alert for its Tokyo metropolitan area as summer heat continues to bake many parts of the country, according to the Ministry of the Environment.

Cities of Tokyo, Saitama, Chiba, Yokohama, Mito, Utsunomiya, and Maebashi are expecting a dangerous level of heatstroke risks, as the ministry issued a red alert for heatstroke, the highest in its five-tier warning system.

The ministry advises people in these areas to avoid going outdoors and halt all exercise except for special cases, as the actual temperature is much higher than the skin temperature.

Japan's weather agency issued heatstroke alerts on Thursday for eight prefectural regions, including Iwate and Fukushima, with temperatures as high as 35 degrees Celcius.

The country's heatstroke warning system is based on the Wet-Bulb Globe Temperature index, one of the empirical indices representing the heat stress to which an individual is exposed, including temperature, humidity, and the amount of solar radiation.

A reading above 31 is labeled "danger," indicating high heatstroke risks.