Eight people have been killed in the massive blizzard in the United States bringing more than 2ft (60cm) of snow.
Six states have declared states of emergency, and thousands of flights have been cancelled.
More than 50 million people across more than a dozen states have been warned to stay at home as it moves north.
The nation's capital, Washington, could lie under a record 30in (76cm) of snow by the time the storm passes on Sunday.
The weather system affects a huge swathe of the country, from Arkansas in the south to Massachusetts in the north-east.
Supermarkets ran out of food amid a rush for supplies before the first snowflakes fell on Friday.
In summary:More than 7,000 flights have been cancelled for Friday and Saturday More than 100,000 homes lost power in North Carolina The US federal government closed down at noon on Friday President Barack Obama is to remain at the White House, officials said Eight people have been killed in car crashes in Tennessee, North Carolina, Kentucky and elsewhere States of emergency have been declared in Tennessee, North Carolina, Virginia, Maryland, Pennsylvania, the District of Columbia, and parts of other states Washington's transport system - the second busiest in the US - will close all weekend Many events, including two sold-out concerts by singer Garth Brooks in Baltimore, have been postponed
Washington's mayor, Muriel Bowser, said this was a major storm with "life and death implications".
The National Weather Service (NWS) warned that the worst of the snow would fall in the Washington area from the early hours of Saturday to the early afternoon, with winds of more than 50mph (80kph).
In a warning at 02:17 (07:17 GMT), NWS tweeted that an "intense snow band" was moving through the area.
A webcam of Washington's National Mall showed the "near-whiteout conditions" the NWS warned of.
Residents in the capital and surrounding suburbs in Virginia and Maryland have been warned the snowfall could eclipse the district's record of 28in that fell during a two-day period in 1922.
As the weather system approached the country's most populous city, New York Mayor Bill de Blasio urged residents to be ready.
New Jersey Governor Chris Christie, a Republican presidential candidate, returned from the campaign trail in New Hampshire to take charge of snow preparation.
The US capital feels like a city in hiding. Residents have been told to find a safe place and stay there until the storm has passed. The streets are empty and restaurants, bars and supermarkets remain closed.
Public transport is at a standstill and over 6,000 flights have been delayed or cancelled. Officials warned anyone trying to travel in the blizzard risks getting stuck for hours, marooned or killed.
Catholics in Washington, Baltimore, and Delaware were told by archdiocese officials that missing Mass this Sunday was excusable given the terrible conditions.
Supermarket shelves in many areas were laid bare. In Baltimore, shopper Sharon Brewington remembered how she and her daughter were left with just noodles and water when the last big snowstorm struck in 2010.
"I'm not going to make that mistake again," she said.
NWS director Louis Uccellini said the system had "the potential of being an extremely dangerous storm that could affect over 50 million people".