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WATCH: Rare Tidelike Fog Washes Over Grand Canyon

In a rare event late last week, visitors to Grand Canyon National Park were able to see fog roll into the canyon like a tide, blanketing the popular tourist attraction.

The phenomenon was caused by a temperature inversion, or simply, a reversal of normal air temperatures, which allowed a shallow layer of cold air sit at ground level and warmer to hover above it.

"With just enough moisture on the ground from rain a week prior, the air at the bottom of the canyon cooled more rapidly, causing fog and a strong inversion to form," Expert Meteorologist Brett Anderson said.

The inversion trapped the fog like a ‘lid' on the canyon, Anderson said.

While it's rare for clouds to blanket the canyon in this way, it is not unheard of. This is the second year in a row that the phenomenon made its appearance across the canyon.

‘It's back," the National Park Service said of the event on Facebook.

"The clouds were trying to settle in the canyon for the past couple of days, but today we're getting a real show," they wrote Thursday.