Sustained snow since late January has buried northern communities like Aomori under drifts of around two metres (six feet) that left residents struggling to leave home and forced schools and businesses to close.

But the temperature rose Wednesday, reaching 8C in Aomori, increasing the risk of chunks of heavy, wet snow dropping from rooftops, potentially causing injuries and even death, officials said.

"We ask affected residents to be careful and stay mindful of falling snow and avalanches," Deputy Chief Cabinet Secretary Masanao Ozaki said at a press briefing.

By Wednesday, extreme snowfall had killed 35 people and caused 393 injuries across the country since January 20, according to the Fire and Disaster Management Agency.

Many of the cases involve mounds of snow falling on residents from houses or people tumbling from their roofs while trying to clear it.

Aomori's accumulated snow on the ground fell below 1.6 metres on Wednesday for the first time in four days, but traffic chaos continued, according to local broadcaster ATV.

Television images showed residents walking along narrow paths carved between massive walls of snow, standing twice as high as people.

In the Niigata region, facing the Sea of Japan, a man was found dead on Tuesday at his collapsed house under heavy snow, while another man died after his garage caved in, Fuji Television said.

The government has deployed troops to help clear huge drifts in northern regions.

Weather forecasters warn that cold weather will return from the weekend and bring further snow to northern cities.