Snow, icy rains and strong winds chilled the US north-east and parts of Canada on Thursday, raising the death toll to nine from a severe winter weather system.
The winter storms, which earlier swept through the US south and the lower Great Lakes region, have sparked air travel chaos and downed power to hundreds of thousands of homes.
In the north-east, Maine and parts of New York state, Vermont and New Hampshire were blanketed in up to 35 centimetres of snow, while rain soaked the Atlantic coast, said AccuWeather.com.
An additional 10 to 20 centimetres or more of snow were expected in some locations, the National Weather Service said.
According to media reports, the deaths included two children, aged one and two, in a car accident on an icy road in Arkansas.
A man and a woman were crushed by a truck after they lost control of their scooter on a slippery street in Indiana. Two others died in accidents in Oklahoma, while falling trees also claimed lives in Texas and Louisiana.
More than 2,000 flights were cancelled as people tried to travel after the Christmas holiday.
Wind gusts felled trees and power lines in Connecticut, and nearly 300,000 homes were without power in the mid-west and south, said broadcaster ABC.
The storm system gathered strength early in the week, spawning at least 30 tornadoes on Tuesday in the US south, according to CNN.
The port city of Mobile, Alabama, was particularly hard hit by a tornado that struck a hospital, a high school and a historic church, the Press-Register newspaper reported.
Little Rock, the capital of Arkansas, a state that normally gets no snow, had the whitest Christmas in 90 years, receiving 20 centimetres.
A second snowstorm was expected to sweep across the mid-west and the east coast before New Year's Eve, AccuWeather forecast.