Atlantic Canada is being walloped by two fierce snowstorms that are combining.

One storm hit southern Ontario and Quebec on Friday, leading to at least three Ontario deaths, two on the roads and an 80-year-old woman who was shoveling her driveway. The other is hammering the northeastern United States.

Forecasters are predicting 30 to 40 centimetres of snow today for parts of Nova Scotia and New Brunswick, and up to 30 centimetres for Prince Edward Island.

It appears Newfoundland will get off relatively lightly with up to 25 centimetres of snow by Sunday.

"Just the fact that we have a blizzard warning for such a large area... is something that we haven't seen for the past few years," said Paula Sutherland, a meteorologist with Environment Canada.

"We are looking at blizzard conditions... the snow and blowing snow combined will give poor visibility, at times possibly reduced to zero, throughout the day and evening," she said.

Forecasters say in some parts of Atlantic Canada, the snow will be whipped by winds of up to 100 kilometres an hour, cutting visibility to almost zero.

Dozens of today's flights have been cancelled at Halifax Stanfield International Airport.

Very few cars could be seen on the roads in downtown Halifax Saturday morning as blowing snow whipped through the streets, creating near white-out conditions.

Several businesses were closed or operating on a reduced schedule, including the Nova Scotia Liquor Corporation.

Forecasters also warn there could be some flooding along the Nova Scotia coast between Halifax and Yarmouth.

In the northeastern U.S., half a million homes and businesses are without power because of a powerful storm that has dumped up to half a metre of snow on Connecticut.

People in the Boston area are digging out of 40-centimetres of snow.