Snow rollers in America - what are they?

Snow rollers

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They look like frosted donuts or even snow-covered hay-bales but they are in fact fragile mounds of snow.

They're called snow rollers and they've appeared across fields and parks in America.

They're very rare as it's unusual for the weather conditions to be just right to cause them.

BBC's weatherman Peter Gibbs explains how they are created.

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