A rare type of wave-like cloud was spotted over Victoria on the weekend.

Kelvin-Helmholtz waves could be seen in the sky over Victoria's northern Grampians on Saturday.

Image: Kelvin-Helmholtz waves over Victoria's northern Grampians on Saturday. Photo: Andrea Cooper

These wave-like clouds form when wind near the top of the cloud is moving faster than the wind beneath it, causing 'wind shear' across the cloud top. This wind shear causes waves of cloud to form along the top edge of the cloud, in the same way wind produces waves in the ocean.

Image: Kelvin-Helmholtz waves over Victoria's northern Grampians on Saturday. Photo: Andrea Cooper

Kelvin-Helmholtz waves can form on clouds at various heights in the atmosphere and they are usually short-lived.