New York Mayor Zohran Mamdani has declared a state of emergency, ordering the shutdown of the city’s entire traffic network for all but emergency travel as a severe snowstorm hits the northeast United States.

“NYC, we’ve declared a local state of emergency ahead of this blizzard. Stay safe, New York,” he posted on X late on Sunday.

The National Weather Service (NWS) warned that a severe winter storm would bring heavy snow, strong winds, and coastal flooding from the coastal mid-Atlantic to Maine through Monday.

Snowfall rates of up to 3 inches (7.6cm) per hour will occur at times, with snowfall totals as high as 12 to 24 inches (30.5-61cm), resulting in “nearly impossible travel conditions”, the NWS said. Gusts of up to 60mph (100km/h) were likely late Sunday and into Monday, it added.

Power outages are also anticipated due to strong winds combined with the weight of heavy, wet snow, it added. As of 7:30pm on Sunday (00:30 GMT on Monday), at least 22,895 customers were without power in the state of New Jersey, according to tracking website poweroutage.us.

Blizzard warnings have been issued by the weather service in New York state’s NYC and Long Island; Boston, Massachusetts; as well as coastal communities in New Jersey, Connecticut, Delaware, Maryland and Rhode Island. Emergency declarations were issued in New York and New Jersey in advance of the storm, as officials mobilised readiness efforts.

“It’s been a while since we’ve had a major nor’easter and major blizzard of this magnitude across the Northeast,” Cody Snell, a meteorologist at the NWS’s Weather Prediction Center, told The Associated Press news agency. “This is definitely a major winter storm and a major impact for this part of the country,” he said.

The NWS in Boston warned of a “Potentially Historic/Destructive Storm” southeast of the Boston-Providence corridor, writing on X that it was “very concerned” about heavy snow and winds causing power outages.

On Sunday evening, the storm had already begun to hit New York, reducing visibility to the extent that the skyscrapers of Wall Street were barely visible from the adjacent borough of Brooklyn.

In New York, with a population of more than eight million, Mamdani said streets, highways and bridges would be shut down from 9pm on Sunday (02:00 GMT, Monday) until noon (17:00 GMT) Monday.

“New York City has not faced a storm of this scale in the last decade,” he said, explaining the state of emergency. “We are asking New Yorkers to avoid all nonessential travel.”

The ban will not apply to essential workers or people who need to travel due to emergencies.

Brooklyn resident Brandon Smith, 33, complained that workplaces remained open, even if the roads were not.

“It’s gonna be difficult for most New Yorkers to get around because we still have to go to work. It’s unfortunate roads are suspended as jobs are not gonna stop calling us in,” he told the AFP news agency.