Falling temperatures on the East Coast have put more people at risk in a region already battling petrol shortages, power cuts and spasms of lawlessness in the wake of Superstorm Sandy.
With temperatures near freezing and more than 700,000 people still without power in the area, some who were planning to run in the cancelled New York City Marathon instead headed to the hard-hit borough of Staten Island to volunteer to help storm victims.
Other disappointed runners staged impromptu races of their own. Thousands poured into Central Park shortly after dawn including teams of runners from Italy, Germany and Spain who began running their own personal marathons.
"A lot of people just want to finish what they've started," said Lance Svendsen, the organiser of a group called Run Anyway.
New York Mayor Michael Bloomberg was reluctant to plunge back into a controversy over the last-minute cancellation. He put off questions about the marathon at a briefing on Saturday and focused on what he said were more pressing matters.
"I spoke with many people who were worried and frustrated and cold," Mr Bloomberg said. "There is no power there and temperatures are dropping. Even those who have generators are having a hard time getting fuel."
The city opened warming shelters in areas without power and Mr Bloomberg was urging older residents without heat to move to them. The city also was handing out 25,000 blankets to residents who insist on staying in powerless homes.
"So please, I know sometimes people are reticent to take advantage of services. The cold really is something that is dangerous," he said after a visit to the Rockaways section of Queens, a waterfront area that was slammed by storm surge. Federal officials were to tour parts of the region later on Sunday.
Though New York and New Jersey bore the brunt of the destruction, at its peak, the storm reached 1,000 miles across, killed more than 100 people in 10 states, knocked out power to 8.5 million and cancelled nearly 20,000 flights.
Economic damage was estimated at 50 billion dollars (£31.1 billion), putting the storm among the most expensive disasters in the US.