NEW YORK - More than 35 million people along the Philadelphia-to-Boston corridor rushed to get home and settle in Monday as a fearsome storm brought the potential for hurricane-force winds and 1 to 3 feet of snow that could paralyze the Northeast for days.

Snow was blowing sideways with ever-increasing intensity in New York City by mid-afternoon as flurries began in Boston. Forecasters said the storm would build into a blizzard, and the brunt of it would hit Monday evening through today.

"Expect extremes," said climatologist Cliff Harris, referring to the drastic different weather patterns between the Northeast and Northwest. "Some areas in the Northeast may not even get above zero. Winds of 70 mph are predicted."

As the storm closed in, much of the Northeast began closing. More than 5,800 flights were canceled, and many of them may not take off again until Wednesday. Schools and businesses closed early. Government offices closed. Shoppers getting food stocks jammed supermarkets. Broadway stages went dark.

And cities mobilized snowplows and salt spreaders to deal with a dangerously windy blast that could instantly make up for what has been a largely snow-free winter in the urban Northeast.

All too aware that big snowstorms can make or break politicians, governors and mayors moved quickly to declare emergencies and order the shutdown of highways, streets and commuter railroads - perhaps for days - to prevent travelers from getting stranded and to enable plows and emergency vehicles access.

"It is not a regular storm," New York Mayor Bill de Blasio warned in ordering city streets closed to all but emergency vehicles. "What you are going to see in a few hours is something that hits very hard and very fast."

Boston was expected to get 2 to 3 feet of snow, New York 1 to 2 feet and Philadelphia more than a foot. The National Weather Service issued a blizzard warning for a 250-mile swath of the region, meaning heavy, blowing snow and potential whiteout conditions.

On the snowy Metro-North commuter train platform in White Plains, N.Y., postal worker Peter Hovey said he will be playing it safe when he has to deliver packages today.

"If you're telling me the trains might not run tomorrow, I'm telling you this: I'm not driving," he said. "It's going to be ridiculous out there, frightening."

Even if they wanted to, many people won't be able to hit the roads.

New York Gov. Andrew Cuomo declared a state of emergency and announced a travel ban on all Long Island roads. The governors of Massachusetts and Connecticut similarly slapped restrictions on nonessential travel.

New York City began reducing subway service, and commuter railroads across the Northeast announced plans to stop running in the evening. Most flights from the region's major airports - including New York City's La Guardia and Boston's Logan - were canceled and probably won't resume until Wednesday.

Nicole Coelho, 29, a nanny from Lyndhurst, N.J., was preparing to pick up her charges early from school and stocking up macaroni and cheese, frozen pizzas and milk at a supermarket. She also was ready in case of a power outage.

"I'm going to make sure to charge up my cellphone, and I have a good book I haven't gotten around to reading yet," she said.

Shopping cart gridlock descended on Fairway, the gourmet grocery on Manhattan's Upper West Side. The meat shelves were all but bare, customers shoved past each other, and outside on Broadway, the checkout line stretched for a block as the wind and snow increased. Store employees said it was busier than Christmas.

In yet another possible sign that people were hunkering at home, Fresh Direct, a grocery delivery service in the Northeast, said it had seen a rise in orders for "movie-day" snacks such as microwave popcorn and chocolate chip cookies.

On Wall Street, however, the New York Stock Exchange stayed open and said it would operate normally today as well.

Coastal residents braced for a powerful storm surge and the possibility of damaging flooding and beach erosion, particularly in New Jersey and on Cape Cod in Massachusetts. Officials in New Jersey shore towns warned people to move their cars off the streets and away from the water.

Utility companies across the region put additional crews on standby to deal with anticipated power losses.