Japanese weather officials are urging people to prepare for heavy snow and cold temperatures as soon as possible. They warn that the coldest air mass of this winter is expected to bring heavy snow to much of the country from Tuesday.

The Meteorological Agency said on Monday that snow has already started falling in northern parts of the country along the Sea of Japan, and mountainous areas in Shikoku due to the low-pressure system.

The agency also forecasts that a cold air mass will flow into northern and western Japan from Tuesday through Thursday. This is expected to bring heavy snow and snowstorms to the Japan Sea coast from northern to western Japan. If the snow clouds linger, they could dump a large amount of snow in a short time.

Officials say low-lying areas on the Pacific side of Kyushu and Shikoku may also have heavy snow.

In the 24 hours to noon on Wednesday, 70 to 100 centimeters of snow is expected in Niigata Prefecture, 70 to 90 centimeters in Hokuriku, 60 to 80 centimeters in Tohoku and Kanto-Koshin, and 50 to 70 centimeters in Kinki and Chugoku. Tokai may have 40 to 60 centimeters, Hokkaido and northern Kyushu, 30 to 50 centimeters, Shikoku, 20 to 40 centimeters, and southern Kyushu, 10 to 20 centimeters.

Weather officials say winds will intensify across the country, and rough waves are expected offshore from Tohoku to Okinawa and Amami.

On Wednesday, temperatures are expected to plunge to minus 12 degrees Celsius in Sapporo, minus 9 in Nagano, minus 6 in Sendai and minus 3 in Tokyo.

The Meteorological Agency warns that snowstorms could disrupt transport and cause power outages. Water pipes could also freeze.

It says residents of areas where heavy snow is expected should avoid going out if possible.