Lenticular clouds
Because of their shape resembling lenses, lenticular clouds are commonly called UFO cloudsMet Office

Residents in Cape Town were amazed to see several unidentified flying objects hovering over their city over the weekend. Those were special clouds that look like alien spaceships but actually are not.

The South African city witnessed a phenomenon that forms what is called lenticular clouds. Lenticular clouds are saucer-shaped clouds that form in the troposphere when the air is stable over the mountains and winds blow from the same or similar direction, according to meteorologists.

"As the wind blows across hilly or mountainous regions, the air undulates in a downstream train of waves. If there is enough moisture in the air, these waves will condense to form the unique appearance of lenticular clouds," the Met Office explains.

Because their shape resembles lenses, lenticular clouds are commonly called UFO clouds and this is believed to be one of the most common explanations for UFO sightings across the world.

Cape Town goes into a frenzy over UFO clouds

Sighting of the UFO clouds that formed over Table Mountain drove residents into social media frenzy as they posted photos of the distinctive natural phenomenon.

The base of the lenticular clouds is at around 6,500-6,500ft from the Earth's surface, according to Met Office. "The clouds can be seen as far as 60 miles downwind of the hills or mountains that led to their formation," it notes.