Japan's weather officials are warning of dangerously high temperatures in some parts of the country on Tuesday.

The Japan Meteorological Agency says it expects high temperatures due to a high-pressure system over mainly eastern and western Japan.

Daytime highs are expected to reach a dangerous 38 degrees Celsius in the cities of Hamamatsu and Kochi.

They are forecast to climb to 37 degrees in central Tokyo, Kofu, Okayama and Kagoshima cities. Temperatures will likely rise to 36 degrees in the cities of Sendai, Nagoya and Kyoto and 35 degrees in Kobe and Fukuoka cities.

The agency and Environment Ministry have issued heatstroke alerts for 31 prefectures from the Kanto-Koshin to the Kyushu regions.

People are advised to avoid unnecessary outings, use air conditioners without hesitation and frequently take in fluids and salt. Special attention should be paid to elderly people and infants as they are at higher risk of developing heatstroke.