WASHINGTON — A massive winter storm swept across much of the United States over the weekend, disrupting power supplies and air travel, prompting emergency declarations across large swaths of the country, and warnings that cold may linger.

Forecasters ? ?said snow, sleet and freezing rain, with dangerously frigid temperatures, would sweep the eastern two-thirds of the nation on Sunday and into the week.

Calling the storms "historic", US President Donald Trump on Saturday approved federal emergency disaster declarations in 12 states.

Seventeen states and the District of Columbia have declared weather emergencies, the Department of Homeland Security said.

In Georgia, the state's senior meteorologist, Will Lanxton, forecast the storm could bring "perhaps the biggest ice storm we have expected in more than a decade" followed by unusually cold temperatures.

The National Weather Service also warned of widespread, heavy ice accumulation in the Southeast, where "crippling to locally catastrophic impacts" can be expected.

The sprawling storm system has taken a heavy toll on the US power grid, particularly in the South.

As of Sunday morning, more than 500,000 customers were without electricity, according to PowerOutage.com, with more than 100,000 each in Mississippi, Texas, and Tennessee.

"We do have tens of thousands of people in affected states in the South that have lost power," DHS Secretary Kristi Noem said late on Saturday afternoon.

The Department of Energy on Saturday issued an emergency order authorizing Texas grid operators to deploy backup generation resources at data centers and other major facilities, aiming to prevent widespread blackouts.

Flight cancellations

Air travel has also been severely disrupted. At least 13,500 flights have been canceled across the US since Saturday, according to flight-tracking site FlightAware. More than 9,600 of those were scheduled for Sunday. Aviation analytics company Cirium said its data shows that Sunday would be the highest cancellation event since the pandemic, with over 29 percent of all departing flights axed.

Major carriers including Delta Air Lines, JetBlue and United Airlines warned passengers to brace for further cancellations and abrupt schedule changes. Significant disruptions were also expected at major airport hubs in Dallas-Fort Worth, Charlotte, Philadelphia and Atlanta, home to the nation's busiest airport.

The brutal storm is the result of a stretched polar vortex, sending Arctic cold across North America. Scientists say the increasing frequency of such disruptions of the polar vortex may be linked to climate change, though the debate is not settled and natural variability plays a role.

Authorities warned of life-threatening cold that could last a week post-storm, with wind chills in the Northern Plains and Upper Midwest dipping below — 45 C.

Agencies Via Xinhua