A huge snowstorm brought chaos to the United States' east coast Monday, canceling thousands of flights, closing schools and forcing the postponement of coronavirus vaccinations as New York City steeled itself for possibly one of its heaviest ever snowfalls.

The National Weather Service (NWS) issued storm warnings from Virginia to Maine -- home to tens of millions of people -- as heavy snow mixed with wind gusts up to 50 miles (80 kilometers) per hour spurred blizzard-like conditions along the eastern seaboard.

New York declared a "state of emergency" that restricted non-essential travel, moved all children back to remote learning and rescheduled long-awaited vaccine shots as the city braced for almost two feet (60 centimeters) of snow.

Salt trucks and snow plows moved out across New York's streets, already quieter than usual due to Covid-19, as Mayor Bill de Blasio announced that the few children who had returned to pandemic-era classrooms would also stay at home on Tuesday.

"There will be locusts, next, at the rate we're going," quipped de Blasio, who also suspended outdoor dining in the latest blow to the city's beleaguered pandemic-hit restaurants, on MSNBC. 

More than 1,600 US flights were canceled -- mostly at airports in New York, Boston, Philadelphia and Washington -- disrupting travel that has already been heavily curtailed by the pandemic.

Airlines canceled all flights in and out of LaGuardia Airport and JFK Airport, while 71 percent of flights were scrapped at Newark Liberty Airport.

- 'Dangerous' -
Covid-19 vaccinations for New York City were also to be halted on Tuesday.

"This is a dangerous, life-threatening situation," New York Governor Andrew Cuomo told reporters.

By 4:00 pm Monday, 15.3 inches of snow had been recorded in Central Park, according to the NWS, with eight inches falling in just six hours.

Snowfall was expected to continue into Tuesday morning, with forecasters predicting 20 inches in total before the storm moves northeast through New England.

If that much falls in the Big Apple, then it would become the city's eighth-biggest snowstorm since records began in 1869.

"This is expected to be one of the bigger snowfall events for New York City," Matthew Wunsch, a National Weather Service forecaster, told AFP.

The most snowfall to have blanketed America's commercial capital was 27.5 inches, over three days, in January 2016.

In Washington, where snow and ice formed since Sunday, President Joe Biden postponed a scheduled visit to the State Department due to the conditions.

- Closed roads -
The capital pushed back until Tuesday a planned return to school for tens of thousands of children who have been learning at home for almost a year because of the pandemic.

Heavy snowfall also lashed New Jersey, Philadelphia and Connecticut.

New Jersey issued a state of emergency, allowing authorities to close roads, evacuate homes and commandeer equipment needed for public safety. 

"This storm is going to get worse before it gets better," tweeted Governor Phil Murphy, adding that six vaccination mega-sites in the state would remain closed Tuesday.

Philadelphia also declared a snow emergency, closing city government buildings for Monday and ordering residents to move their cars off snow emergency routes so the plows can get through.

In a suburb of Wilkes-Barre, Pennsylvania, a couple in their fifties were shot dead by their neighbor during an argument about moving snow in front of their house, the local police chief told AFP.

The shooter took his own life as police arrived to arrest him, he added.

The storm hit mountainous parts of California with more than six feet of snow and heavy rain last week.

It then moved to the Midwest, dumping about eight inches of snow in Chicago, according to the NWS.