The US northeast has been battered by heavy snow and strong winds as a mighty storm carved a violent arc across several states, killing more than a dozen people and snarling holiday travel.
More than 3000 flights have been cancelled since Christmas Day including 746 on Thursday, as the storm wreaked havoc from the Gulf of Mexico to the Great Lakes before heading northeast, according to tracker FlightAware.
In New York City, high winds caused major air traffic delays: 186 flights were cancelled outright at the three major airports - Kennedy, LaGuardia and Newark.
"Winter weather has arrived for many parts of the state, so as a precaution we have opened the emergency operation centre to co-ordinate response efforts using all state and local resources," New York governor Andrew Cuomo said.
New York Mayor Michael Bloomberg used residents still without power two months after deadly superstorm Sandy slammed into the city in October to seek refuge in emergency shelters.
Although the storm was winding down late on Thursday, a warning for heavy snow remained in effect overnight in New Hampshire and western Maine, the National Weather Service said.
The storm was departing the region, the government forecasters said, "but not before dumping another six to eight inches (15 to 20 centimetres) of snow over portions of Maine."
So far, the heaviest snowfall has been recorded in northern New York, with 40 centimetres on the ground in the town of Edwards, near the border with Canada.
And a new storm was already looming, forecast to hit portions of New England, the mid-Atlantic, and the Ohio valley in the last weekend of 2012, according to forecasters at Accuweather.com.
The building storm was predicted to bring more snow, including to regions that only got rain in the first onslaught, the forecasters said.
In Canada, dozens of planes were grounded in Toronto, Ottawa and Montreal due to the wintry weather, with 45 centimetres of snow expected in the southern part of Quebec province.
Earlier in the week, nearly three dozen tornadoes were reported in the southern US states of Texas, Louisiana, Alabama and Mississippi.
More than 200,000 people lost power in Arkansas, Mississippi and Texas, and Entergy, the regional utility company, warned on Wednesday it could take crews up to a week to restore electricity in all areas.
The governors of both Mississippi and Alabama have declared states of emergency.
In Indiana, authorities dispatched nearly 600 trucks to clear highways and smaller state roads, and advised travellers to stay home if possible or else leave themselves extra time.
The storms have claimed at least 13 lives - three in Arkansas, two each in Oklahoma, Indiana and Virginia, and one each in Louisiana, Ohio, Pennsylvania and Texas - according to an AFP tally of official and media reports.