Japanese weather officials are warning of torrential rain in the Kanto-Koshin region through Wednesday due to unstable atmospheric conditions.

They are calling on the public to be on the alert for swollen rivers and possible flooding in low-lying areas, as well as lightning, gusty winds and hail.

The Meteorological Agency said a front near Kanto that brought downpours to Nagano Prefecture is making the atmospheric conditions in the region unstable.

The front is expected to move northward late on Tuesday, causing warm and damp air to flow toward the front and making atmospheric conditions extremely unstable in the Kanto-Koshin region through late Wednesday.

Through Wednesday morning, the region may be hit by as much as 30 milliliters of rain with thunder per hour.

The agency says a warning could be issued if the rain clouds develop more than expected or continue to stay over the area.

Weather officials advise people to take shelter inside sturdy buildings if there are signs of cumulonimbus clouds approaching, such as sudden cool winds.

Meanwhile, a high-pressure system is forecast to cover the Kanto-Koshin region from Friday through Tuesday, likely raising temperatures in some places to 35 degrees Celsius or higher.

The agency has issued a high-temperature warning and is urging people to be on the alert for heatstroke.