Blizzards have caused road chaos across North America

Snow, sleet and rain slammed into Canada and the north-eastern United States in the worst storms this winter.

At least 12 people have died in the blizzards, which have caused traffic chaos on dangerous, icy roads.

Hundreds of flights were cancelled in New York, Washington, Chicago, Toronto, Montreal and Ottawa, and meteorologists say the deep freeze is set to continue.

The storms sent a chill through the hearts of many couples on an icy Valentine's Day, delaying flower and gift deliveries.

"I'm afraid I'll go out of business. I have $38,000 worth of flowers, but I've only sold $7,000 worth," Florist Karen Pell told Reuters news agency in Indianapolis.

At least 300,000 households were without electricity from Virginia to New Jersey, power companies said.

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Washington was also hit, with federal offices opening late and 2008 Republican presidential contender Mitt Romney forced to cancel a campaign appearance in New Hampshire.

The snow storm started in the US Midwest on Tuesday, leaving an icy trail of destruction as it blanketed the north-eastern states on Wednesday.

Up to 65cm (25.5 inches) of snow was expected in both Quebec and Vermont, while about 70 National Guard troops have been deployed in Oswego County in upstate New York, which was buried in 3m (10 feet) of snow earlier this week.

As it recovers from Hurricane Katrina, the Gulf Coast was also hit by the severe weather. Thunderstorms lashed the region and a tornado killed one person in Louisiana.

More than 50 people have died in the US since the cold snap first hit in January.