More than 50 million people have been warned of a “potentially paralysing storm” late on Friday that will bring 24in (60cm) of snow within hours.
There are warnings the blizzard could cause power outages and will bring road and air travel to a halt.
A rush for supplies led to long queues and empty shelves at supermarkets.
The weather system has already proved to be deadly, with two drivers killed in North Carolina, one in Tennessee and a pedestrian dead in Maryland.
- States of emergency declared in Maryland, North Carolina, Georgia, Pennsylvania, Virginia and the District of Columbia
- Blizzard watches in effect from Arkansas through Tennessee and Kentucky and as far north as New York, according to the National Weather Service
- Heaviest snowfall (24ins) predicted for area just west of Washington DC, with 1 to 3in an hour forecasted to fall
- The capital’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, and schools across the region are closed on Friday
- Airlines have issued waivers for travel, meaning passengers can rebook – and more than 2,500 flights have been cancelled, according to FlightAware.
High winds could compound problems, with 30mph (50km/h) winds forecast for Manhattan on Saturday, and even stronger gusts in Washington and Baltimore.
New York Mayor Bill de Blasio urged residents to be ready.
“We’re bracing for the first big storm of the winter. I want to let my fellow New Yorkers know we’re prepared, the agencies here are ready for what’s coming up ahead,” he said.
New Jersey Governor Chris Christie, who is running for president, says he will remain on the campaign trail despite the fact his state is in the path of the storm.
Mr de Blasio said that the governor should “come home”.
National Weather Service director Louis Uccellini said the system had “the potential of being an extremely dangerous storm that could affect over 50 million people”.
He added: “We are talking about a potentially paralysing storm that is already setting up.”
The record snowfall for Washington is 28in (71cm) that fell during a two-day period in January 1922.
Boston, which bore the brunt of repeated snowstorms last year, is expected to escape relatively lightly this time, with just a few inches.
A light dusting of snow on Wednesday night caused gridlock in Washington, raising fears about what lies ahead.
Routine commutes lasted up to three hours and some people abandoned their cars, after an inch fell – a fraction of what is expected on Friday and Saturday.
Washington Mayor Muriel Bowser tweeted an apology and even President Barack Obama’s motorcade got snarled up in it, spending an hour and 12 minutes on 15-mile (24km) journey from Andrews Air Force Base to the White House.