TOKYO: Heatstroke alerts were issued for Japan's capital Tokyo as well as its surrounding Saitama, Chiba and Ibaraki prefectures on Monday for the first time this summer season as sweltering weather continued to prevail.

The mercury soared as scorching heat gripped the regions on Monday, according to the Japan Meteorological Agency (JMA), with temperatures reaching 35 degrees in Tokyo, also this summer's first.

The high temperatures as of 11:30 a.m. were 36.4 degrees Celsius in Otsuki city, Yamanashi prefecture, 35.7 in OmecCity, 35.6 in Kasama city, Ibaraki prefecture and 35.2 in central Tokyo, reports Xinhua news agency.

Weather officials added that humidity is also high, warning people of heatstroke risks.

The high temperatures and moist air flowing in could cause localised downpours, said the JMA, forecasting hourly precipitation of up to 60 mm in the northern Kanto region and 30 in southern Kanto.