NEW YORK -- Coastal residents of New York and New Jersey faced new warnings to evacuate their homes and airlines cancelled hundreds of flights as a new storm arrived Wednesday, only a week after Superstorm Sandy left dozens dead and millions without power.

Forecasters said the latest storm appeared weaker than first thought, but it still carried the threat of high winds, storm surges and even snow that could cause further damage to the already weakened infrastructure of the country's most densely populated region. Rain and wet snow started falling in New York City around midday, with the worst expected in the afternoon.

"I am waiting for the locusts and pestilence next," New Jersey Gov. Chris Christie said. Public works crews with heavy machinery worked to build up dunes to protect the battered shoreline.

Exactly as authorities feared, the storm brought down tree limbs and electrical wires, and utilities in New York and New Jersey reported that some customers who lost power because of Sandy lost it all over again as a result of the nor'easter.

More than half a million homes and businesses remained without power as temperatures hit freezing at night, and finding tens of thousands of people emergency housing -- in some cases, for the long term -- was the greatest challenge.

New York Mayor Michael Bloomberg ordered police to use loudspeakers to warn vulnerable residents, many of them in low-income public housing, about evacuating.

"Even though it's not anywhere near as strong as Sandy -- nor strong enough, in normal times, for us to evacuate anybody -- out of precaution and because of the changing physical circumstances, we are going to go to some small areas and ask those people to go to higher ground," Bloomberg said Tuesday.

But many were deciding to stay, worried about their empty homes being looted. Others decided the situation couldn't get much worse.

"We're petrified," said James Alexander, a resident of the hard-hit Rockaways section of New York City where many homes burned to the ground during Sandy. "It's like a sequel to a horror movie." Nevertheless, he said he was staying to watch over his house and his neighbours.

The Federal Emergency Management Agency put a number to the storm's homeless in New York and New Jersey, saying 95,000 people were eligible for emergency housing assistance. Just under a million people were still without power in the region.

Storm surges along the coasts of New Jersey and New York were expected to reach perhaps 3 feet (0.9 metres), only half to a third of what the hurricane-driven Sandy caused last week. But Sandy destroyed some protective dunes, especially in New Jersey, making even a weaker surge dangerous.

High winds, which could reach 65 mph (104 kph), could stall power restoration efforts or cause further outages.

Major airlines cancelled flights in and out of the New York City area ahead of the storm. Sandy last week led to more than 20,000 flight cancellations.

New York City was closing all parks, playgrounds and beaches and ordering all construction sites to be secured. Tuesday evening, Bloomberg ordered three nursing homes and an adult care facility evacuated from Queens' vulnerable Rockaway Peninsula.

New York Police Commissioner Raymond Kelly said it wasn't wise to stay put. "I think your life is more important than property," he said.