Over 175,000 people were without power from Missouri to Virginia as of Monday afternoon, while more than 2,400 flights were cancelled and thousands more delayed, according to tracking websites Poweroutage.us and FlightAware.

The National Weather Service (NWS) predicted up to a foot of snow in Washington, where Congress nonetheless met to certify Donald Trump's election victory, four years to the day after his supporters stormed the US Capitol to try to overturn his 2020 loss.

A White House spokesman said President Joe Biden was closely monitoring the severe weather and was ready to support affected states.

The US capital's brightly-colored row houses and normally leafy streets were blanketed with white on Monday as residents waded through snow and slush, while schools were closed for at least a day in a city which only rarely has to face such wintry conditions.

The storm tracked eastward after bringing blizzard conditions to states including Kansas and Missouri.

- Lethal conditions -

At least five people have been killed so far in storm-related incidents.

The Missouri State Highway Patrol has reported two fatalities, both of whom were killed after being struck separately by sliding vehicles they had exited.

The state agency said late Sunday on its Facebook page that it had responded to over 1,000 stranded motorists and 356 crashes.

In neighboring Kansas, two people were killed after the vehicle they were traveling in spun out on a highway, while another person was killed after colliding with an out-of-control tractor trailer, the state's highway patrol reported.

Kentucky Governor Andy Beshear in a Monday morning update urged residents to continue to stay home.

"Remember, this is a significant snow and ice event, so the roadways are still dangerous," he said.

Video clips from Kansas showed cars skidding off ice-coated highways and tractor trailers jack-knifing.

Scientists say extreme weather is becoming more common and more severe as a result of manmade climate change.

The NWS warned thunderstorms could impact southeastern states, bringing hail and tornadoes, and that accumulations of thick ice -- as well as widespread tree damage from powerful wind gusts -- could lead to prolonged power outages.

Temperatures are expected to plunge, in some places reaching below zero degrees Fahrenheit (minus 18 degrees Celsius), while strong wind gusts compound the dangers.

The mercury could sink tens of degrees below seasonal norms on the US Gulf Coast.

Conditions could prove especially perilous in the Appalachian mountain region, where a deadly hurricane in late September devastated communities and ravaged multiple southeastern states including Kentucky.

The system was also blasting chilly winds across the Great Lakes into New York, where some areas have received multiple feet of so-called lake effect snow.

Several governors and local officials, including in Kentucky, Missouri, Virginia and Maryland have declared states of emergency and urged residents to stay home while emergency management works to clear roads.