A snowplow clears snow in front of the Federal Hall National Memorial in New York, the United States, on Jan. 4, 2018. New York State Governor Andrew Cuomo has declared state of emergency for the entire downstate region on Thursday as a snow storm continued to pound the U.S. East Coast. (Xinhua/Wang Ying)

Backgrounder: What is a "bomb cyclone"?

WASHINGTON/NEW YORK, Jan. 4 (Xinhua) -- An intense "bomb cyclone" pummeled the U.S. East Coast on Thursday with high winds and heavy snowfalls, leaving thousands of flights cancelled, schools and offices closed, and millions of Americans bracing for power shortages.

Snow plows and salt trucks rumbled down streets and highways as the powerful winter storm that has hammered the South swept across the Northeast, cloaking much of the region in a white haze.

More than 44,000 Americans were left without electricity, at least 8 million people are under blizzard warnings, and 58 million are in the path of this bitter winter storm, according to a CNN report.

Most of them were in the states of Virginia and North Carolina, where more than 31,000 people had no power.

Nearly 10,000 have lost power in the Boston area, while in New York City, more than 3,500 people are without power.

North Carolina Governor Roy Cooper said Thursday three people have died in the snow storm. A cold snap gripping a large part of the country had already been blamed for a dozen earlier deaths.

U.S. forecasters called the ongoing winter storm a "bomb cyclone" for its rapid and rare drop in atmospheric pressure. The storm is crawling up the northeastern American Thursday morning with a threat of winds gusting as high as 60 mph and a bone-chilling blast of Arctic air.

Through Thursday, parts of New York could see five to nine inches of snow, Philadelphia three to six inches and Washington one to two inches. In New England, Boston and Providence, Rhode Island, could get eight to 12 inches, while Portland, Maine, could see 10 to 15 inches, the U.S. National Weather Service said.

The service also said Atlantic City could record up to 18 inches of snow, Delaware beach towns were facing the prospect of a foot of snow and travel has become "very dangerous to impossible" in the highly populated Hampton Roads region of Virginia, which could receive up to 12 inches of snow in places.

More than 3,000 flights were cancelled on Thursday, with airports in New York and New Jersey; Boston reporting the most cancellations, according to FlightAware, an aviation tracking website.

The agency that runs New York City-area airports says all flights have been suspended temporarily at JFK and LaGuardia airports due to wind and whiteout conditions.

At Newark Liberty airport in New Jersey, airlines had cancelled 867 flights as of noon Thursday, 73 percent of normal flight activity.

The winter storm that is slamming U.S. East Coast also led to more than 200 flight cancellation in the midwestern city of Chicago.

According to Chicago Department of Aviation, by 9:30 a.m. local time, Chicago O'Hare International Airport had cancelled more than 180 flights and the Midway Airport, more than 50 flights.

In Washington D.C., the federal government delayed opening offices on Thursday as blowing snow swirled in the capital. The Office of Personnel Management informed that nonemergency federal workers could report two hours late, work remotely, or take an unscheduled leave.

Power firms have warned of possible fuel shortages to come since heating units in homes and commercial buildings running furiously to fend off the deep freeze.

Some experts said the extreme weather was a result of climate change.

"It is often difficult for public to link global warming to living environment, because the process between the two are non-linear," Yifang Zhu, associate director of Center for Clean Air and professor of Department of Environmental Health Sciences at University of California, Los Angeles (UCLA), told Xinhua.

"Global warming doesn't just mean warming," said Zhu. "It means the average temperature on Earth, including the ocean and the atmosphere, is increasing year by year."

While the globe is becoming hotter on average, this temperature increase can have paradoxical effects, such as more extreme snowstorms, she said.

"Extreme weather is one of the impacts of global warming. As the planet warms, many already-dry areas are becoming even drier. Many extremely cold areas are becoming even colder. Hurricanes in Texas is becoming more intense."

Many governors or local leaders have declared emergencies, and blizzard warnings were in effect in Delaware, Maine, Maryland, Massachusetts, New Jersey, Rhode Island and Virginia. New York Governor Andrew Cuomo declared a state of emergency for all of downstate New York.

The advancing storm first landed in the southern United States on Wednesday. Three cars on an Amtrak train carrying more than 300 passengers from Miami to New York derailed Wednesday night in snow-covered Savannah, Georgia. No injuries were reported.

The "bomb cyclone" storm is expected to continue to affect eastern North America into the weekend.