US president Barack Obama warned the threat from ex-hurricane Sandy was "not yet over" as Americans confronted the devastation caused by one of the biggest storms in the country's history.
Large areas of New Jersey were devastated by flooding and parts of New York City were at a virtual standstill after the storm hit, bringing with it a record 4-metre-plus tidal surge.
At least 45 people were confirmed to have been killed by the storm, which had earlier killed more than 60 in the Caribbean.
Millions of people are facing the possibility of days without power in plummeting temperatures.
In Queens, an entire district of around 80 homes was destroyed in an inferno which was sparked by an electrical fault as the storm hit, while New Jersey's governor described the devastation caused by flooding in Atlantic City as "unthinkable".
The storm was tracking north-west on Tuesday (US time) and was heading towards Canada, bringing heavy rain and snow to areas in its path.
With just a week to go until election day, Mr Obama was due to visit storm-hit areas of New Jersey on Wednesday while rival Mitt Romney, who had earlier converted one of his Ohio rallies into a storm relief fundraiser, was resuming campaiging in Ohio.
Look back on how events unfolded as the US woke up and surveyed the damage from the huge storm. (All times AEDT):
3:10pm: The official dubbed the "recovery tsar" for New Orleans after Hurricane Katrina is on his way to New York to help authorities deal with the impact of superstorm Sandy.
Professor Edward Blakely spoke to The World Today and warns there could still be more deaths on the US east coast because critical infrastructure like power, water and mass transportation has been so badly affected.
Professor Blakely told Tanya Nolan it could be up to a month before "hard" electricity infrastructure is back to full capacity.
"You have to restore power because New York City is high rise buildings. These high rise buildings house a lot of the population, and they cannot go up and down elevators. Many of these people are over 50, so movement of them is critical.
"The other thing is food - unless you have power, you don't have food. You have to keep the food cold and alive.
"So these are really emergency issues - as a matter of fact they're rescue issues - because if you don't have food and power, your chances of surviving are very low."
3:00pm: Foreign Minister Bob Carr says Australia has offered to help with the storm clean-up efforts.
He says there are 24,000 Australians living or travelling in areas affected by the storm, but so far there have been no reports of injuries or other mishaps.
"An exercise where we send people across who can both help and learn would be useful. Disaster management and recovery is something of an Australian speciality.
12:37pm: New York's JFK airport is expected to reopen on Wednesday (US time).
12:20pm: The aftermath of Sandy looks set to dominate the final week before the US presidential election.
Barack Obama is set to tour disaster areas in New Jersey on Wednesday while Mitt Romney is back campaigning in Florida.
The ABC's US election analyst John Barron says that "on balance, at the moment it is advantage Obama but there are potential downsides for the next week as well."
He says Obama's situation is "high risk, high reward"
12:04pm: The New York Stock Exchange is expected to reopen on Wednesday (US time). The US dollar has slipped against the euro after Sandy forced a two-day trading shutdown - the first since the 'Great Blizzard' of 1888.
11:40am: Correspondent Ben Knight says people are still trapped in flooded homes in New Jersey, 24 hours after the storm hit. Parts of New York are getting back to normal, while the clean-up is underway in lower Manhattan.
11:25am: Atlantic City tavern owner Monty Duhn has told ABC News 24 about looking up and seeing the eye of the storm as it slammed into New Jersey:
"It was pretty much over us. I could actually see a little red sky and stars. I looked up and it was actually kind of nice. That lasted for a good 15-20 minutes, maybe half an hour, and then you slowly felt it coming and we got the tail of the hurricane and it really hit."
11:09am: This video shows New York mayor Michael Bloomberg surveying the damage in Breezy Point, Queens, where dozens of houses were destroyed by a fire which broke out as the storm hit:
10:53am: High winds, flooding, storm surges and fires have left a trail of destruction across the north-eastern United States after Sandy hit.
Use the map below to see the spread and scale of damage. (Place markers are approximate.)
10:36am: "The devastation is unthinkable," New Jersey governor Chris Christie said after seeing pictures of the New Jersey shore.
10:32am: LATEST: The death toll has climbed to at least 40 people this morning; 18 of them in New York City; insurers say the damage bill could run to $US15 billion.
10:29am: It was billed as the Halloween 'Frankenstorm'; and now Sandy has forced the cancellation of New York's annual Halloween parade.
"For the first time in our 39-year history, the mayor's emergency management and the NYPD have cancelled the parade," organisers said in a statement on their website.
10:20am: Americans have started assessing the damage caused by the superstorm, which has left New York City and New Jersey in shock.
9:54am: New York mayor Michael Bloomberg has toured some of the worst affected areas, including the scene of a fire which destroyed at least 80 homes in Queens.
"To describe it as looking like pictures we've seen of the end of World War II is not overstating it, the area was completely levelled, chimneys and foundations were all that were left of many of these homes."
9:26am: WEATHER UPDATE Post-tropical cyclone Sandy is now travelling north-west across Pennsylvania and is likely to move into Canada on Wednesday (US time).
The National Hurricane Centre says it is continuing to bring strong winds, heavy rain and snow to northern parts of the US.
It is packing winds of 72 kilometres per hour
Rainfall of up to 12 inches is expected across New Jersey, Delaware, Maryland, northern Virginia and southern Pennsylvania.
Snowfall of up to 10 inches are likely in the mountains of West Virginia into far western Maryland
Falls of up three feet are likely over the central Appalachians and falls of two feet over Kentucky and the mountains of North Carolina/Tennessee border
Dangerous surf conditions will continue from Florida through to New England for the next few days
Meteorologist Kevin Walsh says heavy rain will now be the main threat as the storm system travels inland.
9:21am: Barack Obama's response to the disaster has been praised by NJ governor Chris Christie - a staunch Mitt Romney supporter.
"The president has been all over this, he deserves great credit," Mr Christie said. "He gave me his number at the White House, told me to call if I needed anything, and he absolutely means it."
9:14am: Manhattan's flooded Battery Tunnel has become the Big Apple's latest tourist attraction, correspondent Lisa Millar says:
9:08am: NYC mayor Michael Bloomberg has given an update on the disaster response. Here are some key points:
18 people have been confirmed dead in New York City so far
Coney Island hospital is being evacuated
64,000 people still in NYC evacuation centres
4,000 yellow cabs now operating on NYC streets
Public schools will remain closed on Wednesday (local time)
Building inspectors assessing in Manhattan
Mr Bloomberg is urging people to stay safe as the city cleans up.
"Winds are still high. Trees are very waterlogged, more limbs and whole trees can come down. Stay away from city parks," he said.
8:50am: North America correspondent Lisa Millar is in New York City, where huge amounts of water are still swilling around the subway system.
"I've spent the last four five hours down in lower Manhattan where there is absolutely no mobile phone access.
"It's very difficult to get around. The subway is still shut down. I think what I've found most extraordinary is how high the water mark is down there, how much water there still is flooded into the tunnels in subways, which is why they're not even putting a timeline on when they're going to be able to reopen that critical public transport system for New York."
8:45am: Sandy: They said it:
8:30am: Former Age journalist Nick Miller is in New York and described the scene there this morning:
8:27am: The US National Weather Service says the storm brought a record surge of almost 4.2m to Manhattan - above the previous record 3m, set during Hurricane Donna in 1960.
8:00am: New York mayor Michael Bloomberg says in Manhattan is stable.
The crane, on West 57th Street, buckled in the gale force winds as the storm hit.
When the winds die down, Mr Bloomberg says authorities will try and strap the boom to the building until a secondary crane can be erected to help dismantle the damaged crane.
7:44am: Atlantic City residents describe the force of the storm:
7:31am: STORM STATS
Highest rainfall recorded at Andrews Air Base in Maryland with 388mm
Highest wind gust was 151 kilometres-an-hour
Highest snowfall was 66 centimetres in Maryland
7:20am: New York firefighters have described the blaze that razed 80 homes in Queens during the height of the storm:
7:12am: Australia's ambassador to the US, Kim Beazley, has told ABC News24 there are thousands of Australians in the disaster zone.
But he says very few Australians have needed consular assistance since the storm hit.
"Most people have been aware of what was about to happen to them. There've been very clear instructions of how to behave," he said.
"We're not getting too many reports of Australians placed in a situation where they haven't been able to effectively look after themselves.
"Quite frankly the consular burden on us has been very light."
But he says authorities are overwhelmed by the destruction.
"When the Atlantic Ocean decides to move onshore there's not a huge lot you can do about it except wait to clean up the consequences," he said.
7:00am: Lower Manhattan residents are being warned they may be without power for four days.
Electricity provider Consolidated Edison (Con Ed) says almost 250,000 homes are still without power in Manhattan.
"This is the largest storm-related outage in our history," a spokeswoman said.
"We try to restore lines that will get power to the most customers possible, but it will depend on the equipment."
The blackout area includes some NYC's wealthiest neighbourhoods, including Tribeca, Chelsea and Gramercy Park.
The ABC's Ben Knight is in the area and describes the scene:
"Everywhere you look here in Lower Manhattan there are trucks and men in hard hats beginning the cleanup of the city. And it's going to be a massive job," he said.
"There are hundreds of generators that are suddenly out running pumps starting to get the water out of shops and sewers, tunnels and underground car parks.
"On the streets, rubbish and debris are scattered all over the footpath. This is a bleak city the day after the flood and it's going to be some days before New York will even begin to return to normal."
6:52am: UPDATE death toll rises to 35 across US and Canada. Authorities still expect it to climb further.
6:42am: Here's US president Barack Obama's address from Red Cross headquarters in Washington:
6:32am: Barack Obama will travel to New Jersey on Wednesday (US time) to view damage caused by Sandy.
The White House has issued a statement:
"Tomorrow afternoon, the president will travel to New Jersey where he will join governor (Chris) Christie in viewing the storm damage, talking with citizens who are recovering from the storm and thanking first responders who put their lives at risk to protect their communities."
6:17am: COMING SOON: We will be bringing you video of Barack Obama's address from the Red Cross headquarters in Washington.
6:00am: The ABC's Ben Knight is in New York and describes the scene:
"It's the middle of the day on a week day here in Manhattan but it looks more like a Sunday morning," he said.
"Every shop south of 42nd Street is shut and dark, except for those that have brought in generators to pump out the flood water.
"The scaffolding lying on the ground and the roads and footpaths are covered with a rainbow coloured film of oil that has been washed in from the harbour and the tunnels.
"Tourists are wondering around taking photos. The locals simply look stunned."
5:55am: US president Barack Obama has visited the headquarters of the Red Cross in Washington and warns the storm is "not yet over":
"It is still moving north. There are still communities that could be affected. So I want to emphasize there are still risks of flooding, there are still risks of downed power lines, risks of high winds."
5:49am: Devastating aerial footage from the National Guard as they search from a helicopter for victims in the New Jersey town of Seaside Heights:
5:30am: ELECTION UPDATE: The campaign has been put on hold as US president Barack Obama and Republican candidate Mitt Romney deal with the disaster.
Barack Obama is at the White House leading the government's emergency response. He has declared a major disaster in New York City and has ordered the recovery to start immediately.
"I want everyone leaning forward on this. I don't want to hear that we didn't do something because bureaucracy got in the way."
Mitt Romney has attended a rally converted into a storm relief event in swing state Ohio.
"A lot of people are hurting this morning. They were hurting last night, and the storm goes on."
5:00am: It is nearly 2:00pm on Tuesday afternoon in the United States and many east coast residents have started cleaning up as the floodwaters from superstorm Sandy subside.
Some insurers are estimating the total damage bill could top $US10 billion.
4:50am: UPDATE The death toll from the superstorm is now at least 32 across the US and Canada.
NYC mayor Michael Bloomberg says as rescue and recovery efforts continue, the toll is likely to rise.
"Tragically we expect that number to go up."
4:43am: Across the border, Canadians felt the force of Sandy and more than 100,000 residents in and around Toronto are still without power.
One woman was killed during the storm after she was struck by a sign in Toronto shopping mall car park.
4:22am: UPDATE: in the fire that tore through the New York neighbourhood of Breezy Point during the superstorm.
New York mayor Michael Bloomberg says firefighters are still dousing flames in the flooded neighbourhood but the blaze is now under control:
"Winds were just devastating, blowing [fire] from one building to the next one and those buildings were close together."
4:12am: UPDATE New York Stock Exchange and the Nasdaq say they will reopen Wednesday.
4:08am: Video: NYC residents venture outside to check out the damage around Union Square. This footage was captured by Storyful's Aine Kerr:
3:58am: From the photo desk: Rescue workers are evacuating stranded residents, including many elderly people and young children, from their flooded homes in New Jersey.
3:45am: New York mayor Michael Bloomberg says the damage to the city's power grid and transport system is "unprecedented".
"The work of getting our power grid restored however is going to take more time and a lot of patience," he said.
"MTA's CEO Joe Lhota has described this as the worst disaster the agency has seen in the 108 years the subways have been running and Con Ed has described the damage done to its power systems as unprecedented in scope."
3:30am: New Jersey governor Chris Christie has given an update on the level of destruction in his state.
He says the level of devastation on the Jersey Shore is "unthinkable".
"The devastation is unprecedented, like nothing we've ever seen reported before."
NJTV Online has broadcast part of his press conference:
3:12am: US president Barack Obama has held a video-teleconference with top officials in the situation room of the White House on the latest developments associated with Sandy.
"During the briefing, the president expressed his concern for those impacted by the storm, as well as the heroic first responders who are selflessly putting themselves in harm's way to protect members of their communities," a White House statement said.
"He also noted his sadness over the loss of life associated with the storm so far.
"The president told his team that their top priority is to make sure all available resources are being provided to state and local responders as quickly as possible and directed them to identify and resolve any potential bottlenecks or shortfalls should they arise."
The president has also postponed campaign events in the vital swing state of Ohio.
3:08am: New York City mayor Michael Bloomberg says that power is likely to be out for two or three days in most areas.
Hundreds of thousands of homes are without power in New York City, while nearly 2 million are without power across the state.
"We expected an unprecedented storm and that is what we got," he said.
2:40am: The US Coast Guard is still searching for the captain of the replica HMS Bounty, which .
Fourteen of the 16 crew were saved from the water in a dramatic helicopter rescue, while one of the crew members was unconcious upon being plucked from the ocean and was later pronounced dead.
1:40am: The first pictures have emerged from the devastating Breezy Point blaze, which saw more than 50 home razed when fallen power lines started a fire:
1:07am: US president Barack Obama has gotten an endorsement from unlikely place, with Chris Christie, the Republican governor of New Jersey, lavishing praise on Mr Obama for his handling of the disaster:
The president's been great... I spoke to him three times yesterday, he called me for the last time at midnight last night, he asked me what I needed.
Mr Christie said that he asked the president to cut through bureaucratic "mumbo jumbo" and help New Jersey, and he "got on it":
"The president has been all over this, he deserves great credit ... He gave me his number at the White House, told me to call if I needed anything, and he absolutely means it.
"It's been very good working with the president, and his administration has been coordinating with us great - it's been wonderful."
12:25am: New Yorkers are waking up to scenes of destruction, with water still inundating parts of the city:
11:45pm: New Jersey's main power company is reporting that the country's oldest nuclear power plant has been safely shut down and is currently stable.
There were concerns earlier after impact from the storm made most of the its water circulation pumps unusable.
PSEG Nuclear said it manually shut down its Salem plant on the Delaware River, but said there were "no issues" in the shutdown.
11:10pm: Joe Lhota, the chairman of the New York Metropolitan Transport Authority (MTA), has told US media it is too early to tell how long it will be before the subway system is back up and running.
Mr Lhota says they will be assessing the situation over the rest of the day, but that it is likely that there will be no public transport until bus services resume on Wednesday at the earliest.
He says the MTA will be re-routing New York City's 4,000 buses to help commuters without the subway system, and has asked for patience from the 8 million people who use public transport every day:
"Given the extent of the problem it is too soon for me to put any timeframe on it. I want New Yorkers to think about how big our subway system is, how robust it is."
"We were hit last night by the most devastating storm we could possibly imagine."
10:50pm: New York Mayor Michael Bloomberg is warning that while the worst of the weather is over, the situation still remains dangerous:
"The worst of the weather has come and the city certainly is feeling the impacts."
"We have seen record surge levels - we're seeing an extraordinary amount of water throughout lower Manhattan."
Mr Bloomberg says about 250,000 homes are still without power in the city:
"There are trees down throughout the city... power outages on an extremely wide basis. The latest estimates show roughly quarter-of-a-million customers without power."
10:42pm: The US National Weather Service has issued a blizzard warning for parts of West Virginia as Sandy moves further inland.
More than 30 centimetres of snow has been reported at lower elevations in the state, with at least 128,000 homes without power.
10:10pm: Hundreds of thousands of people along America's east coast have spent the night in evacuation shelters.
Anna-Kate Twitty from the American Red Cross says they are doing everything they can to make evacuees comfortable:
"The Red Cross is operating shelters all along the east coast so our main priority right now is making sure that our shelter residents have a safe place, a hot meal, and a cot to sleep on."
9:55pm: Disaster modelling expert Richard Fenning predicts the economic cost of the storm could be as high as $20 billion.
But Mr Fenning says New York in particular will be well equipped to deal with the clean-up:
"You can't control the weather, certainly not in this instance, but what you can do to a certain extent is control your own reaction to that," he said.
"New York particularly is a city that's had, with September 11, enormous experience dealing with something that literally comes out of the blue and hit the city in a very significant way."
9:30pm: A firefighter who attended the blaze in the Queens suburb of Breezy Point says they had to rescue dozens of people trapped inside burning homes:
"We were able to transport the people from the rear apartment to the front of the apartment, down the stairs and into the boat. There was probably 25 people in the boat."
The blaze started after high winds knocked down power lines.
9:10pm: New York governor Andrew Cuomo tweets that at 6:00am (local time) '1,943,572' New Yorkers are without power.
9:05pm: A levee has broken in northern New Jersey, flooding the towns of Moonachie, Little Ferry and Carlstadt with 1.5 metres of water.
8:58pm: North America correspondent Michael Brissenden is in Boston at the northern end of the storm:
8:45pm: US president Barack Obama has declared a 'major disaster' in New York after the storm.
8:40pm: ABC correspondent Ben Knight spoke to 7.30 from a shelter in Delaware:
8:25pm: The New York Fire Department has confirmed that the 50 homes destroyed were at Breezy Point, one of New York most remote neighbourhoods.
The fire was still not under control at 5:00am (local time).
Local television showed pictured of firefighters wading through waist-deep water, and using inflatable boats to reach the blaze.
There are reports more than 40 people who defied mandatory evacuation orders had to be rescued.
8:05pm: The ABC's Ben Worsley explains why Sandy is such an unusual and dangerous storm system:
8:00pm: Fire has broken out in the New York City borough of Queens, destroying 50 homes.
7:55pm: PM spoke to Australian expat Phillip Dundas, who lives in Manhattan.
Mr Dundas says New York has been plunged into darkness:
"We have a view from our apartment which is about 41 floors up, and all over Manhattan and Brooklyn and the entire island of Manhattan, but for a few of the real namesake skyscrapers, it is completely black.
"I can see from right down town in Battery Park and the World Trade Centre, all the lights are out there. And then looking right through to mid town, the lower east side, the East Village, Chinatown and various bridges, the Williamsburg Bridge, the Manhattan Bridge, the Brooklyn Bridge, they've all lost their power. All the lights are off."
7:50pm: Earlier Maryland governor Martin O'Malley said the storm has left its mark on the state, with hundreds of thousands left without power:
"We have power outages that are climbing to above 300,000 people without power and we expect that to go up to a million as the sound of trees cracking all over Maryland becomes the sound of this dark and stormy evening."
7:30pm: ABC correspondent Ben Knight is in Delaware, where he spoke to locals who had gathered in an evacuation centre in the town of Rehoboth Beach.
Ronald Roswell left his home in Rehoboth Beach at the height of the storm, when his apartment building flooded.
His mother drove his family to the shelter before returning to the apartment to ride out the storm:
"It was a treacherous out really. The rain was coming down sidewards, blowing the car sideways. You could hardly see out the windows but we made it here safely," Mr Roswell said.
"Really we didn't think it was going to be too bad but it started to get worse so my dad and mum were like 'do you all want to go to a shelter with your kids and your girlfriend?' So I was like 'yes'."
Mr Roswell said he felt safe because the area had not been hit by a storm of this magnitude in over 70 years, but he now fears for his mother's safety:
"Last time it hit was when my grandmother was young. It was about 1938 it hit here."
"I'm worrying about her, [my mother] right now. I want to see if I can use somebody's phone to call her again. I just pray to God you know everybody's safe out there and it clears over."
John Mulvey is the shelter's doctor, and said his experience as a responder to Hurricane Katrina meant he had an idea of how bad the storm could be:
"I think part of why Hurricane Katrina was so deadly was because there were about a dozen or so hurricanes that were going to hit New Orleans and didn't."
"So to a certain extent there was a bit of jadedness on the part of folks in New Orleans. I responded to Hurricane Katrina and I saw how confusing it can be to deal with that and I made a promise to myself that I wasn't going to let that happen in Delaware
Take a look back at our of the disaster
© ABC 2012
16:28 EDT Hail is caused when raindrops are lifted up into the atmosphere during a thunderstorm and then supercooled by temperatures below freezing, turning them into ice balls.