NASA astronaut Scott Kelly tweeted an image of the blizzard, engulfing much of the United States and in particular, the Eastern Seaboard, from the International Space Station.
A state of emergency was declared in Washington D.C. and New York City, as well as in Tennessee, North Carolina, Virginia, Maryland, Pennsylvania, New Jersey and parts of other states.
Up to 2ft of snow has fallen in cities across the east coast, with as much again forecast to fall by today.
Meteorologist Ryan Maue, of WeatherBell Analytics, said 80 million people were affected, and a quarter of the US is now blanketed by snow.
He said: “This is going to be one of those generational events, where your parents talk about how bad it was.”
There were thousands of road crashes in the treacherous conditions. Some 7,600 flights were cancelled – about 15 per cent of those scheduled – according to the flight-tracking service FlightAware.
Dozens of flights to and from the UK were among those grounded.
Hurricane-force winds of 75mph were recorded at Dewey Beach in Delaware, and at Langley Air Force Base in Virginia.
Life-threatening blizzard conditions were expected to persist throughout the weekend.
The long-anticipated storm has started to look even bigger than forecast, with increased snowfall now predicted.
That included up to 2ft expected in Washington, Baltimore and Philadelphia and more than 1ft for New York.
Some areas outside the major cities could get up to 2.5ft.
NWS winter storm expert Paul Kocin, who co-wrote a two-volume textbook on blizzards, said: “This is kind of a top ten snowstorm, and for New York and Washington this looks like top five. It’s a big one.”
The National Guard was called to help motorists stranded along parts of the Pennsylvania Turnpike near the Allegheny Mountain Tunnel in Somerset County.
In the Washington metro area, nearly 2ft of snow had fallen by yesterday morning.
The federal government closed its offices at noon on Friday, and all mass transit was due to remain closed until tomorrow.
In Silver Spring, Maryland, where about 20in of snow had fallen, lightning flashed and thunder rumbled.
Other states that got more than 6in included Delaware, Georgia, North Carolina, New Jersey, Ohio, Pennsylvania, South Carolina, Tennessee and West Virginia.
In New Jersey, 40,000 people were without power early yesterday, most of them along the coast.
About 1,000 track workers were deployed to keep New York City’s subway system moving and 79 trains had “scraper shoes” to reduce the icing on the rails.
Virginia State Police reported nearly 1,000 crashes and had assisted nearly 800 disabled vehicles.
• The YouTube video shows a timelapse of snow falling in Purcellville, VA