At least 28 dead across multiple U.S. states amid winter storm

At least 28 weather-related deaths were reported Monday as a massive winter storm hit dozens of U.S. states over the weekend, causing widespread power outages, flight cancellations and school closures.

As of Monday afternoon, more than 5,200 flights traveling into, from and within the United States were cancelled and over 6,600 were delayed, according to flight-tracking service FlightAware.

Snow is also expected along the Appalachian region, while rain will spread along the Southeast coast as a cold front moves offshore, the agency said.

Boston's Logan International Airport, Dallas Fort Worth International Airport and New York's John F. Kennedy International Airport were among the hardest hit.

Major U.S. carriers rolled out sweeping travel waivers and flexible re-booking options to assist passengers whose travel plans were disrupted by the cancellations.

However, airline operations remain highly interconnected, with cancellations leaving aircraft and crews out of position and complicating recovery efforts.

The storm also impeded road travel. The Federal Emergency Management Agency warned that driving conditions could become dangerous as blizzard-like conditions, strong winds and ice spread further.

Meanwhile, hundreds of thousands of customers across several U.S. states – from Tennessee to the Carolinas – reported power outages, with Tennessee reporting the highest number of cases.

More than 820,000 customers were without electricity as of early Monday, according to data from PowerOutage.us.

(With input from agencies)