Large snowroller
Credit: aceshot1/Shutterstock

Residents in Wales were in for a surprise on Monday after a weekend of freezing temperatures and blizzard-like conditions left the hoods of their cars covered in perfectly rolled snow formations that look like they were carved into place.

People began posting photos of the fascinating formations, which resemble rolled-up carpets, on Facebook.

The arrangements are appropriately called snow rollers, a rare natural phenomenon that only happens when you have a precise set of weather conditions.

Snow rollers form when you have strong winds that are able to pick up moist snow and blow it along the ground, creating a cyclical effect that rolls the snow, according to The Weather Channel.

Besides this combination, snow rollers also require an existing icy or crusty snow cover to prevent sticking, and the snow needs to be on a sloping surface.

While rare, snow rollers have been spotted in a variety of locations, Ottawa, Canada, and across the Midwest in the U.S.

The snow spirals can range in size and get as large as barrels in some cases, according to The Weather Channel.

When the rolls move, they leave a trail in the snow, similar to how mysterious moving rocks have been known to leave long stretches of trails along the grounds of the Racetrack at Death Valley National Park.