Hundreds of thousands of people were ordered to leave their homes for higher ground, schools and businesses were shuttered and the New York City subway stopped running Sunday as the Northeast prepared for a massive storm packing high winds, floodwaters and even snow.
Watch live pictures from along the East Coast as this enormous storm moves inland.
"We have to take this seriously," President Obama said as he joined federal officials in warning of the unusual and extreme weather threat to 60 million people along the densely populated region from the Mid-Atlantic to New England coasts.
Weather forecasters said Sandy, a late-season hurricane that killed more than 60 people in the Caribbean, was churning up the Atlantic and expected to make a left turn toward the U.S. coast, putting it on a collision course with cold weather from the north and west.
That rare convergence set the stage for what forecasters called a superstorm with destructive force that could be felt as far inland as Chicago and the Great Lakes, 700 miles from the New Jersey shore where Sandy was expected to come ashore late Monday night or Tuesday morning.
High winds extended more than 500 miles from Sandy's center, where sustained winds of 75 mph made it a Category 1 hurricane. The storm's size meant it would be felt across a broad region. Forecasters said the storm could bring as much as 2 feet of snow to higher elevations in West Virginia, Virginia, Kentucky and North Carolina. The National Weather Service warned that waves of 20 to 25 feet were possible on Lake Michigan by Tuesday.
Meteorologist Mike Smith of AccuWeather said damages, including losses to the economy, could top $100 billion -- "worse than Katrina," the killer 2005 storm that struck the Gulf Coast.
New York Mayor Michael Bloomberg ordered evacuation of low-lying areas of the city where 375,000 people live, and thousands more were told to evacuate coastal areas from Maryland to Connecticut. The New York Stock Exchange canceled floor trading Monday.
More than 6,800 airline flights were canceled by Sunday evening, FlightAware.com said. New York, Philadelphia and Washington were shutting down mass transit systems, and schools were closed Monday in those cities as well as Baltimore, Boston and elsewhere.
New York's subway, which handles 8.5 million passengers daily, faces flooding if a storm surge tops Manhattan flood walls, 5 feet above sea level, Weather Underground meteorologist Jeff Masters said.
William M. Welch