The force of Sandy, already a menacing storm system, will be multiplied as it combines with several systems to potentially wreak havoc from North Carolina to New England as far west as the Great Lakes.
The Northeast has been paralyzed by the impending storm. The stock market is closed today, the first unscheduled, market-wide close since September 2001, according to the NASDAQ website. Also in New York, the city's public transportation has been completely shutdown for the second time in history. The first time was for last year's Hurricane Irene.
By morning, waves were already washing over the seawall and into Battery Park at the southern tip of Manhattan, the country's financial center. The city's utility, Consolidated Edison, said it could be forced to shut off power to the financial district if the area becomes inundated.
"It's already at Irene levels and the question is going to be what level the surge will take us to later on this afternoon and this evening when it's actually high tide," New York Gov. Andrew Cuomo said at a news conference today.
The turbulent weather has brought much of the region's transportation to a halt. Paralyzed airports have stranded people all over the country. Over 10,000 flights have been cancelled so far, according to Flight Aware. It is grounding planes throughout Europe since they can't land at their U.S. destinations.
Roads are shut down. Delaware Gov. Jack Markell banned vehicles on the state's roads except for emergency and essential personnel, according to ABC News' Philadelphia affiliate WPVI.
Connecticut Governor Dannel Malloy has ordered road closures for all state highways today, according to ABC News' New York station WABC. The closures will be implemented in two phases. Trucks will be prohibited from operating on limited access highways at 11 a.m. and state highways will be closed to all non-emergency vehicles at 1 p.m.
Tens of thousands of people in coastal areas have been ordered to evacuate their homes before Hurricane Sandy pounds the eastern third of the United States.
States of emergency were declared from North Carolina to Connecticut.
West Virginia Gov. Earl Ray Tomblin declared a state of emergency as rain and snow fell on the state, with snowfall expected to exceed two feet.
Sandy will meet up with cold front coming from the northwest and a high pressure system from Greenland, fueling it with enough energy to make it more powerful than Hurricane Grace, the so-called "Perfect Storm" in 1991, meteorologists say.
"The size of the storm is going to carve a pretty large swath of bad weather," Rick Knabb, director of the National Hurricane Center, said. "This is not just a coastal event."
ABC News' Alyssa Newcomb, Russell Goldman, Sydney Lupkin, Genevieve Shaw Brown and Serena Marshall contributed to this report