On Boxing Day, American relief workers counted the dead from a severe winter storm that had hit the United States for several days, and particularly affected a county in western New York State, where authorities confirmed on Monday at least 25 deaths.

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This border region of Canada has been buried under meters of snow, and has been experiencing frigid temperatures since last week.

The death toll in Erie County on Sunday evening was already 13, but local services have since confirmed the deaths of 12 more people, “bringing the total blizzard fatalities to 25,” said Monday morning during a press conference Mark Poloncarz, responsible for this county.

Some people have been found dead in their cars, and others have died of cardiac arrest trying to clear snow while temperatures are still freezing, he said.

“Your veins shrink, which makes it harder for the heart to circulate blood,” he explained, calling the situation “horrible.”

The total of deaths confirmed by authorities across nine US states is now at least 47 dead. In Ohio, road accidents linked to these bad weather killed nine people, the Ohio State Highway Patrol confirmed to AFP.

The Erie County city of Buffalo is still largely in lockdown due to massive amounts of snowfall, including again overnight Sunday through Monday, Poloncarz warned.

“Please, unless you are part of the emergency services, do not drive,” he asked. "The conditions are bad."

A travel ban was still in effect there Monday morning, but it was defied by some residents, he regretted.

"What we're doing today is getting people to doctors, nurses and hospitals," county sheriff John Garcia told CNN on Monday morning. “The roads are finally starting to be passable because the winds have died down.”

During the height of the storm, rescuers were no longer able to reach people in distress, for example those stranded in their car or at home without electricity.

"It's heartbreaking to have calls from families with kids saying they're frozen," Garcia said.

Electricity has been restored to more than 13,000 homes in the past 24 hours, Mark Poloncarz said Monday morning, but more than 12,000 are still without power. Some will not be able to be connected to the network before Tuesday, he warned.

Since Wednesday evening, the United States has been hit by this storm of rare intensity, whose polar winds have caused heavy snowfall, especially in the Great Lakes region.

Tens of millions of Americans saw their Christmas weekend turned upside down by massive power outages, impassable roads and thousands of canceled flights, causing chaos at airports.

On Monday, more than 1,700 flights were still canceled in the United States, according to the monitoring site Flightaware.com.

Conditions are expected to improve only gradually as the week progresses.

The weather "will continue to cause hazardous travel conditions locally for the next two days," the US Weather Service (NWS) said in its latest national bulletin.

"Most of the eastern United States will remain in freezing conditions through the day Monday, before a more moderate trend sets in from Tuesday," he added.