NEW YORK (AFP) - Two north-eastern United States states banned cars from roads and thousands of flights were cancelled Friday as the leading edge of a blizzard hit with winds forecasted to gust at hurricane-strength.

The storm was forecast to bring the heaviest snow to the densely-populated north-east corridor so far this winter, threatening power and transport links for tens of millions of people and the major cities of Boston and New York.

Governor Deval Patrick temporarily ordered all normal traffic off Massachusetts roads, with the threat of up to a year in jail for violators.

"There are a number of exemptions for... emergency workers and the like. Please exercise caution and use common sense," Mr Patrick said at his emergency centre in Framingham.

In Connecticut, Governor Dannel Malloy issued a "ban on motor vehicle travel on limited access highways" to free up emergency services traffic.

New York and other regional airports saw more than 4,500 cancellations ahead of what the National Weather Service called "a major winter storm with blizzard conditions" along most of the region's coastline.

It came a little over three months after Hurricane Sandy devastated swathes of New York and New Jersey, killing 132 people and causing damage worth some US$71.4 billion (S$88.4 billion).

Snow began in light flurries across the region early Friday, but thickened and by Saturday was expected to leave depths of between half and one foot in New York and as much as two feet in Boston.

The National Weather Service warned that "in addition to the heavy snowfall, wind gusts of up to hurricane force are possible, especially near the coast. This will result in blizzard conditions with drifting and blowing snow."

On Friday night, travel "will be extremely hazardous, if not impossible," the National Weather Service said.

The good news was that the storm's peak was due as the weekend began, meaning far fewer people would be on the roads. Forecasters said the system should blow through on Saturday, with milder temperatures to follow.

Boston was in the bull's eye for the next 24 hours.

Mr Patrick declared a state of emergency, with some 5,000 National Guards soldiers called up, and schools in Boston ordered closed.

Authorities in New York and neighboring New Jersey summoned extra personnel and deployed more than 200 pieces of snow and ice removal equipment in key area airports such as JFK International, LaGuardia and Newark Liberty International.

But JetBlue executive Rob Maruster told NY1 television that the airline was canceling all New York area flights from Friday afternoon through to noon on Saturday.

In addition to mass flight cancellations, the rail service Amtrak said trains from New York northbound and also to the capital Washington, DC, would be suspended later Friday.

Among the more glamorous victims of the travel upsets was designer Marc Jacobs, who had to reschedule his two shows at New York Fashion Week due to "the snow storm in the US and production problems."

New York Mayor Michael Bloomberg, who came under withering criticism for the city's flat-footed response to a blizzard in 2010, said residents should stock up with vital supplies and prepare for the worst.

"Stay off the city streets, stay out of your cars," he said at a news conference.

"Staying off the streets will make it easier for city workers to clear the streets of snow." New York's four zoos also announced they were closing for the duration of the storm.

"You can't take nature too lightly. Hopefully it won't be anything too drastic," Mr Bloomberg said.

Locals were comparing the coming storm to the ferocious Blizzard of 1978, which killed 100 people and buried Boston in more than 68cm of snow and Providence, Rhode Island in nearly 71cm.

During that storm, people were forced to abandon cars stuck on highways and made their way around Boston on cross country skis and snowshoes.