Blizzard conditions were forecast to bring major disruption across the north-eastern United States on Sunday and well into Monday, with a dangerous combination of heavy, wet snow and ferocious winds gusting up to 70mph.

Residents along the east coast scrambled to prepare for the late-winter storm that spurred blizzard warnings from Maryland to Massachusetts, affecting more than 35 million people.

More than a foot of snow was expected, with gales inland and warnings of potential coastal flooding.

The National Weather Service warned that once the storm intensified on Sunday afternoon it could prove significantly more severe than projections that were made just a few days ago.

The weather service said 1 to 2ft of snow was possible in many areas as it put out blizzard warnings for New York City and the Long Island peninsula to the east, for coastal communities in New Jersey, Connecticut, Delaware, Maryland, Rhode Island and, further north, Boston and other parts of Massachusetts.

A storm surge of 2 to 4ft could cause moderate coastal flooding and beach erosion from Delaware Bay to Cape Cod almost 400 miles to the north during high tide cycles.

The storm was projected to arrive on Sunday morning in areas around Washington DC before stretching toward Philadelphia and New York City and reaching Boston in the evening, just as the icy leftovers of last month’s major snowstorm that also brought Arctic temperatures to the region were finally melting away.

The storm could cause whiteout conditions that “will make travel treacherous and potentially life-threatening”, the weather service said, adding that: “The strong winds and weight of snow on tree limbs may down power lines and could cause sporadic power outages.”

Airlines have cancelled more than 6,000 flights in and out of US airports through Monday, according to flight-tracking site FlightAware, with major hubs JFK, LaGuardia, Newark, Philadelphia, Boston Logan the hardest hit.

New York City residents, who were under a blizzard warning for the first time in almost a decade, were urged to stay indoors if possible until the storm passes on Monday. “Staying home means you are staying safe,” mayor Zohran Mamdani told Fox News on Sunday morning.

In a video posted on X at noon, Mamdani announced that public schools would have a “full snow day” on Monday, “no online school, no remote learning, full classic snow day”. He urged children to stay indoors during the height of the storm and to stay safe.

The mayor said the city would expand on efforts it used to deal with a major snowstorm weeks ago. New York had brought in additional snow-clearing equipment from outside the city, Mamdani said, and planned to expand use of geocoding to keep track of bus stops, crosswalks, pedestrian ramps and unsheltered bus stops that need clearing.

A state of emergency was scheduled to begin at noon on Sunday throughout New Jersey, governor Mikie Sherrill announced, with all 21 counties simultaneously under a blizzard warning for the first time on record. Many churches canceled Sunday services and other activities, and officials in Atlantic City urged residents and visitors to its famous casinos to stay off the streets, especially in low-lying neighborhoods prone to flooding.

Sherrill urged New Jerseyans to stock up on food and water, fill their vehicles’ gas tanks, charge their electronic devices and to stay at home if possible.