WE watched in amazement as images of Americans and Canadians shivering through an arctic chill beamed into our homes this week. But we saved the best for last with the latest images coming from Niagara Falls.

Water from the falls literally froze midair as it dropped on Tuesday when the temperature dropped to a record low of -2F (-18C).

GALLERY: FROZEN BEAUTY, NIAGARA FALLS

Images of the falls are circulating online, but beware not all are authentic.

News_Module: Niagara Falls frozen

The cost of the deep freeze has been estimated at US$5b (A$5.63b) - the biggest economic disruption delivered by the weather since Superstorm Sandy in 2012.

While the impact came nowhere close to Sandy, which caused an estimated $US65 billion in property damage alone, the deep freeze's impact came from its breadth.

News_Image_File: Ice, ice, baby ... the frozen falls of Niagara.

"There's a lot of economic activity that didn't happen," said Evan Gold, senior vice president at Planalytics, a business weather intelligence company in suburban Philadelphia.

"Some of that will be made up, but some of it just gets lost."

Gold noted his $US5 billion estimate pales in comparison with an annual gross domestic product of about $US15 trillion - working out to maybe one-seventh to one-eighth of one day's production for the entire country.

"It's a small fraction of a per cent, but it's still an impact," Gold said.

News_Rich_Media: US polar vortex turns Lake Michigan into a sea of mesmerising ice boulders.

Major US airlines, which cancelled about 20,000 flights starting last Thursday, lost anywhere from $US50 million to $US100 million, said Helane Becker, an analyst with Cowen and Co in New York.News_Image_File: A couple look on in awe. Picture: Splash

JetBlue was hit especially hard because 80 per cent of its flights go through New York or Boston, where the carrier shut down on Monday evening and into Tuesday.

The airline also was affected by other airport closures and new regulations limiting pilot hours.

School closures took their own toll, keeping home parents who couldn't find alternatives for their kids.

News_Image_File: Cold snap ... a photographer braves the cold to capture the rare sight.

Even if those parents worked from home, they might not have been as productive, said Tony Madden, regional economist with the Federal Reserve Bank of Minneapolis.

"People in the northern climates are used to dealing with issues of snow and cold," Madden said.

"However, when you get a one-in-20-year event like this, that disrupts activities."News_Image_File: Tourists couldn't believe the sight. Picture: Splash

The insurance industry has yet to estimate costs, but Robert Hartwig, president of the Insurance Information Institute in New York, said insurers plan for about $US1.4 billion in winter storm catastrophe losses in any given year.News_Image_File: Prospect Point at Niagara Falls State Park and Rainbow Bridge where frozen mist and solid ice was visible below. Picture: Splash

"We certainly know there is an epidemic of frozen and burst pipes this week," Hartwig said.

Damage to a Minnesota state health laboratory in St Paul could top $US1 million after the heating system failed and pipes leaked, while Alabama Governor Robert Bentley's home in Tuscaloosa took an estimated $US50,000 blow from a burst water pipe.

News_Image_File: Arctic touch ... Water literally froze midair as the temperature dropped to -2C on Tuesday.

Meanwhile, governments are tallying costs for depleted road salt reserves, blown overtime budgets and repairs.

Other impacts will be felt in about 30 days when high heating bills start coming due, Gold said, which will affect how much consumers can spend in February.News_Image_File: A winter wonderland at Goat Island Park steps in Niagara Falls, Ontario. Picture: Splash

But somebody always benefits, he said.

On-demand cable TV and restaurant delivery services gained, as did home centres and convenience stores where people went to stock up.News_Image_File: A South View of Niagara Falls on January 9, 2014. Picture: Splash

Online retailers benefited from customers with an estimated $US30 billion worth of new holiday gift cards burning holes in their pockets, Gold said.

Other beneficiaries may be farther away, with Boston-based Hopper Research saying the frigid temperatures caused a 52 per cent spike in searches for flights to Cancun, Mexico, from people in Minneapolis and Chicago.News_Image_File: A view of the frozen U.S. Falls frames the city on January 9, 2014 in Niagara Falls. Picture: Splash

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