A fierce winter storm has brought chaos to the northern US, killing at least 11 people and forcing the cancellation of thousands of flights.

More than 61 centimetres of snow fell in parts of Massachusetts town as a state of emergency was declared in New York and New Jersey states.

One worker was killed when a pile of salt being prepared to treat roads in the Philadelphia region fell on him.

A 71-year-old woman suffering from Alzheimer’s disease froze to death after walking out into the cold and getting lost in northern New York state.

At least nine other deaths were blamed on the storm – named Hercules – that caused traffic accidents and other disruption across 22 states and parts of Canada.

Hercules closed major roads for several hours with snowdrifts built up by Arctic winds of up to 105km/h.

Weather experts said the windchill temperature would plummet to -25C in New York state.

More than 4200 international and domestic flights were cancelled at airports along the east coast and as far as Chicago on Thursday night and Friday. Thousands more were delayed.

New York’s John F Kennedy Airport closed for several hours because of poor visibility and high winds.

Flights were also cancelled at Chicago, Boston, Philadelphia and other key airports.

Boston woke up to a temperature of about minus 16C, but with the wind chill, it felt much worse.

Essex county in Massachusetts recorded 61 centimetres of snow. Much of the state’s Atlantic coastline was put on flood alert.

The New York and New Jersey governors ordered major roads closed during the worst of the blizzard, but they were reopened on Friday morning.

However, government leaders appealed for people to stay home unless they had urgent business.

The storm was the first big test for New York City’s new Mayor Bill de Blasio, who took up his job Wednesday.

The mayor urged people to stay indoors.

He shovelled snow from in front of his Brooklyn house on Friday before repeating appeals for drivers to stay off the streets to help the city clear its 9,900km of roads.

“If you want safe, clear streets, stay home,” he said.