Authorities blamed the storm for at least 15 deaths in New York, three in New Jersey, three in Pennsylvania, two in Maryland, two in Connecticut, two in Virginia, one in West Virginia and one on the HMS Bounty replica tall ship. At least one death in Canada was attributed to the storm. Earlier, 67 people died in the Caribbean, bringing the storm's overall death toll to 107.
Sandy, which left at least 7 million people without power and an undetermined number evacuated from their homes, was weakening over Pennsylvania Tuesday, with top sustained winds of 45 mph, the National Weather Service's Hydrometeorological Prediction Center said in its 5 p.m. EDT advisory.
The center of the storm was about 50 miles east-northeast of Pittsburgh. Sandy was moving west-northwest at 10 mph and was expected to turn northwest across western Pennsylvania Tuesday night and then move northward into Canada Wednesday.
National Hurricane Center Director Rick Knabb said in a midday conference call with reporters Sandy's impact along the U.S. East Coast had lessened, but flooding of 2-4 feet was expected in some spots at high tide and wind speeds were "fairly strong" as far west as Lake Michigan.
Knabb said further power disruption could occur Tuesday and "it will take well into [Wednesday] for all of the weather to clear out of the United States."
He said river flooding will be a risk over a large area, particularly in the New Jersey-New York area, because "there is still a lot more rain that could fall."
"I don't want anyone to think the event is anywhere near over," he said.
U.S. Coast Guard Vice Adm. Robert Parker said seas in excess of 20 feet have been recorded on Lake Michigan, and some shipping has been affected because so much water is being displaced, making shipping channels shallower than normal.
Federal Emergency Management Agency Administrator Craig Fugate said response efforts are focusing on life-saving, as well as power restoration, which he said is a public safety issue. He said federal, state and local efforts are also prioritizing getting healthcare systems back online.
Fugate cautioned the public to be careful during the cleanup and rebuilding following the storm.
"The recovery oftentimes results in more deaths and injuries that occur during recovery activities," he said.
President Barack Obama went to American Red Cross headquarters in Washington and cautioned, "This storm isn't over yet."
The president called the storm "heartbreaking for the entire nation" and told those affected by the storm, "America is with you."
He said he has told government officials to do whatever must be done to get help to people as quickly as possible -- with "no bureaucracy. No red tape."
During a call Obama held with governors and mayors from affected areas, several governors offered assistance to hard-hit states, the White House said.
"The president also made clear that his team is working to identify any additional assistance that could further help the state, local, and private sector efforts to bring power back online faster, and that his team would continue aggressively towards this goal," the White House said.
U.S. Transportation Secretary Ray LaHood said Tuesday he will make $13 million in emergency relief funds immediately available to New York and Rhode Island.
The $13 million represents 100 percent of funding the states requested -- $10 million in New York and $3 million in Rhode Island -- the Transportation Department said.
LaHood said the requests were just the first to arrive at the department, and he expects other states to apply for emergency relief funding in the coming days.
"President Obama has directed us to immediately help restore vital transportation infrastructure following this unprecedented and devastating storm -- and that's exactly what we're doing," LaHood said.
The president Tuesday declared a major disaster exists in Connecticut and ordered Federal aid to supplement state, tribal and local recovery efforts in the area, the White House said.
Obama will travel to New Jersey Wednesday, where he and Gov. Chris Christie are to inspect damage, talk with people affected by the storm and meet with first responders.
Sandy left in its path darkened skylines, fires, trees tossed about and streets that became canals. Floodwaters gushed into New York's subway tunnels and scattered parts of the famed Atlantic City, N.J., boardwalk.
Authorities scrambled boats and high-water vehicles to rescue residents trapped in several towns after a berm broke in Moonachie, N.J.
Christie called the devastation to the shorelines of the Garden State, where Sandy made landfall Monday evening, "unthinkable" and asked residents to exercise patience and not return to their homes yet to inspect the damage.
"I know people want to inspect their homes on the barrier islands, but at this point it is unsafe," Christie posted on his Twitter page. "Please be patient."
New York Gov. Andrew Cuomo echoed those sentiments: "If you have been evacuated from #Sandy, return home only when officials say it is safe."
New York's Metropolitan Transit Authority reported on its Twitter page a boat was resting on the tracks at one station.
The MTA said it will resume limited bus service Tuesday at 5 p.m., with fares for passengers being waived until further notice.
MTA Chairman Joseph J. Lhota said in an interview with WNYC, New York, public radio, the city's mass transit system likely would be restored "in pieces and parts" in the next few days.
"We're going to try to be creative," Lhota said.
Governors have declared states of emergency. President Barack Obama signed major emergency and disaster declarations for many states overnight, paving the way for federal assistance. He met with disaster officials again Tuesday morning to assess the situation and monitor recovery efforts.
In Connecticut, CNN reported some residents trapped in their houses by floodwaters received this text message from the state's Emergency Management Office:
"If u find urself surrounded by H2O, call 4 help if u can & then get 2 highest level of home. Hang a white sheet out a street side window."
The water tanker John B. Caddell ran aground in Staten Island, WABC-TV, New York, reported.
An estimated 7.5 million customers were without power in 15 states and the District of Columbia, CNN said, based on numbers it compiled from local power providers.
More than 15,000 flights have been canceled since Sunday because of Sandy, flight tracking site FlightAware.com said.
Amtrak said on its Facebook page it would assess damage to its tracks and then decide when service would be restored.
In West Virginia, where 2-3 feet of snow was forecast, the governor's office asked that only essential state employees report for work.
Forecasters said numerous weather watches and warnings -- including high-wind warnings, storm warnings, blizzard warnings, winter storm watches and warnings, and flood and coastal flood watches, warnings and advisories -- were posted for much of the eastern United States.
New York officials said the Manhattan, Brooklyn, Williamsburg and Ed Koch Queensboro bridges would reopen Tuesday, The New York Times reported. The Tappen Zee Bridge already had reopened.
A spokesman for Consolidated Edison said Tuesday much of Manhattan could be without electricity for several days after an explosion at a substation on the East River Monday.
NewYork-Presbyterian Hospital said it was accepting patients evacuated from other area hospitals, and had canceled all elective procedures and surgeries scheduled for Tuesday.
"Our emergency rooms and dialysis centers are fully operational," the hospital said in a statement. "Patients should confirm all scheduled appointments with their physician's office."
A backup power system failed at NYU Langone Medical Center Monday night, forcing the evacuation of all patients, the Times said.
Medical center officials said the hospital began transporting 215 patients to other facilities Monday evening and was still transporting some early Tuesday.
CNN reported 3 feet of water flowed onto the floor of the New York Stock Exchange building, a first. The stock exchange, which has been closed for two days due to the storm, said Tuesday it will reopen Wednesday.
At least 80 homes burned to the ground in one neighborhood of Queens, fire officials said, though the cause of the blaze was not immediately released.
New York's Metropolitan Transit Authority said seven subway tunnels were flooded, the Metro-North Railroad lost power along some lines, the Long Island Rail Road evacuated its West Side Yards and sustained flooding in one tunnel, the Hugh L. Carey (Brooklyn Battery) Tunnel was flooded, and the Queens Midtown Tunnel took on water and was closed. Six bus garages were disabled by high water.
Some smaller cities north of New York were spared the brunt of the storm but still experienced severe flooding.
Kingston, N.Y., was forced to shut down a sewage treatment plant for about 9 hours after a Hudson River tributary overflowed its banks early Tuesday and breached 7-foot-high berms around the plant, causing a transformer to blow out, city officials said. Officials evacuated residents from waterfront apartments and condominiums. The city is at the confluence of the Hudson River and Rondout Creek tributary.
The storm could cause $10 billion to $20 billion in total economic damages and $5 billion to $10 billion in insured losses, catastrophe-risk modeling firm EQECAT said.