Much of Japan continued to swelter under a blistering heat wave on Saturday.

Weather officials say the mercury was likely to reach at least 38 degrees Celsius in eastern and western Japan and asked people to be vigilant against heatstroke.

A high pressure system covering the archipelago pushed up temperatures from early morning. By noon, Ushiku in Ichihara City, Chiba Prefecture, and Yonago City, Tottori Prefecture, recorded 37.2 degrees.

Daytime highs were expected to reach 39 degrees in Kumagaya City, and 38 degrees in such cities as Kyoto, Saitama, Maebashi and Fukushima.

Heatstroke alerts were issued for 38 prefectures across the country, from the northern prefecture of Hokkaido to the southern prefecture of Okinawa.

The Japan Meteorological Agency warns that the intense heat will continue through Friday next week.

Environment Ministry officials say the death toll from heatstroke tends to surge during heat waves. An increasing number of people have been coming down with heatstroke, and some of them have died.

They advise people to avoid going out unless absolutely necessary, use air-conditioning appropriately and keep hydrated.