At a news conference Sunday, Michael Bloomberg said about 375,000 people in a number of coastal areas including Coney Island, lower Manhattan and parts of the borough of Queens would need to leave their homes. He said those affected would have to stay with family and friends outside of the evacuation area or at one of the 72 shelters the city has set up.
Forecasters said that because of giant waves and high tides made worse by a full moon, the metropolitan area of about 20 million could get hit with a 3.4-metre wall of water.
Sandy, a Category 1 hurricane with sustained winds of 120 km/h as of Sunday evening, was blamed for 65 deaths in the Caribbean before it began traveling northward, parallel to the Eastern Seaboard. As of 8 p.m., it was centred about 780 kilometres southeast of New York City, moving at 24 km/h, with hurricane-force winds extending an incredible 280 kilometres from its centre.
In Washington, U.S. President Barack Obama declared a state of emergency in the District of Columbia and promised the government would "respond big and respond fast" after the storm hits.
"My message to the governors as well as to the mayors is anything they need, we will be there, and we will cut through red tape. We are not going to get bogged down with a lot of rules," he said.
He also pleaded for neighbourliness: "In times like this, one of the things that Americans do is we pull together and we help out one another And so, there may be elderly populations in your area. Check on your neighbour, check on your friend. Make sure that they are prepared. If we do, then we're going to get through this storm just fine."
Officials in New York have ordered the closure of its public transportation system, which began at 7 p.m. ET on Sunday, causing problems for those trying to leave the affected area on buses and subways.
"There really is a timeline when if you don't get there before they stop, you're going to have to find other ways to get out," Bloomberg said. He added that those who stay behind are putting their own lives at risk as well as those of any emergency personnel if they need to enter the affected areas.
The Washington, D.C. metro has also announced a closure of the transporation system starting Monday. It did not mention if they were to remain closed after Monday.
Schools in New York will also be closed on Monday.
Tens of thousands of people were also ordered to evacuate coastal areas across the northeastern United States, including in New Jersey and Connecticut, as officials opened shelters to house the displaced. About 50,000 people in Delaware were told to leave their homes by 8 p.m. ET Sunday.
The New York Stock Exchange and other U.S. financial markets are shutting down Monday. The operator of the NYSE announced the decision late Sunday along with exchange operators Nasdaq OMX Group and CME Group. They said markets might be closed Tuesday "pending confirmation."
NASDAQ is shutting the NASDAQ Stock Market and other U.S. exchanges and markets that it owns. Its exchanges outside the U.S. will operate as scheduled. CME Group will end trading of equity index futures and equity index options on futures market at 8:15 a.m. Central time.
Since the Great Depression, the longest suspension in trading at the NYSE occurred after the attacks on the World Trade Center on Sept. 11, 2001, when the exchange closed for four days.
The United Nations offices in New York will close on Monday and all meetings at the UN headquarters have been cancelled until Tuesday.
Amtrak began cancelling train service Saturday night to parts of the East Coast and planned to suspend nearly all service in the Northeast by Monday night.
Airlines started moving planes out of airports to avoid damage and added Sunday flights out of New York and Washington in preparation for flight cancellations on Monday. According to the flight-tracking service FlightAware, more than 7,200 U.S. flights had been cancelled for Sunday and Monday as of late Sunday evening
An emergency declaration will force the shutdown of Atlantic City's 12 casinos for only the fourth time in the 34-year history of legalized gambling there. City officials said they would begin evacuating the gambling hub's 30,000 residents at noon Sunday, busing them to mainland shelters and schools.
Eastern Canada warned
Canadian officials are urging those in the path of the storm to be prepared.
Environment Canada said heavy rainfall was expected in parts of Ontario and Quebec beginning late Monday or early Tuesday, although the amount would vary greatly according to location. Some regions could see up to 75 millimetres.
The Canadian Hurricane Centre says parts of southern Ontario should brace for 100 km/h winds, especially along western Lake Ontario. Environment Canada said strong winds with gusts exceeding 90 km/h could also batter parts of Quebec.
The Maritimes will also experience some rainfall and strong winds, as well as large waves and pounding surf.
The Canadian Red Cross issued a statement Sunday urging people to prepare for the storm by stocking a number of supplies including water, food, flashlights and a first aid kit. Hurricane Sandy could down trees and power lines and cause flooding, the organization said.
"Be prepared to take care of yourself and your family for at least 72 hours in an emergency," Mike Morton, the Canadian Red Cross director of disaster management in Ontario, said in a release. "By taking some time now to store emergency food, water and other supplies, you can provide for your entire family during a power outage or evacuation."
States of emergency were declared from North Carolina, where steady rains were whipped by gusting winds Saturday night, to Connecticut. Delaware ordered mandatory evacuations for coastal communities by 8 p.m. Sunday.
Environment Canada said wind speeds in excess of 100 km/h were possible in southern Ontario, which could down tree branches and possibly uproot trees. Strong winds could also batter Quebec.
The organization suggested those in the affected areas should pay attention to updates, as the track of the storm could change.
With files from The Associated Press