The snow-weary eastern US is digging out from yet another mammoth storm, as the deadly weather creeps through New England and eastern Canada and another storm approaches.

US media counted up to 21 people dead as a result of the storm, which was blasting New England and eastern Canada with heavy snow and powerful winds, a day after ploughing through southern and eastern US states.

One of the casualties was a 36-year-old pregnant woman, struck and killed by a snowplough in a New York parking lot.

Her baby was delivered alive by Caesarean section but remains in critical condition.

The Canadian weather service predicted up to 50 centimetres of snow in parts of eastern Canada, as flights were cancelled and roads closed on Friday.

Further south, the sun had come out, but roads were dangerously icy as commuters returned to their morning commute.

A series of massive accidents blocked traffic on a major highway, the Pennsylvania Turnpike, and footage from traffic helicopters showed dozens of cars and trucks stuck in pile-ups.

There was to be only a temporary respite for some, with forecasters predicting yet more snow and wintry weather for the US east coast on Saturday.

Nearly 800,000 homes and businesses lost power across 11 states along the eastern seaboard, with 340,000 outages in North and South Carolina, the Department of Energy said on Thursday.

Thousands of travellers have been stranded amid flight cancellations that are expected to last for several days as airlines scramble to clear a backlog.

Broadcasters fell over themselves to find superlatives to describe the “historic” and “mindboggling” “Snowmaggedon”.

The storm is only the latest severe weather to hit the eastern US in what was already the worst winter in 10 years.