Taranaki residents were treated to a rare, if alarming, cloud display at the weekend.

A large cloud formation resembling a UFO was spotted south of New Plymouth sparking a flurry of photographs and comment online.

Rebecca King from Bell Block, south New Plymouth said she was alerted to the cloud when her daughter told her to look out of the window.

“I thought that is amazing,” King told the Herald. “I had to get my cellphone and popped outside to take the photos. I kept going to the window to see if it was still there for about 15 minutes.”

Rebecca King's daughter urged her to look out of the window. Photo / Rebecca King

King posted her photographs to the Extreme Weather Taranaki Facebook page, prompting a chain of comments in a similar vein.

“Aliens,” one poster remarked, and another wrote, “Finally they are here… call MiB (referring to the movie Men In Black”.

Sanity did prevail with Jess Mewes correctly identifying the cloud phenomenon as lenticular clouds.

The MetService explains the formation of these clouds as forming when strong winds blowing across a mountain or mountain range cause waves in atmosphere. Clouds trapped by these waves form distinctive folds that look like flying saucers.

With the prevailing wind coming from a westerly direction in New Zealand the lenticular clouds will most often be seen east of the mountains – in this case, the southeast of Mt Taranaki.

The name lenticular comes from the Latin word lens, meaning lentil-shaped.

Lenticular clouds have also been seen near Mt Ruapehu and in Canterbury when the “norwester” blows.

The formation stuck around for at least 15 minutes. Photo / Rebecca King

A different cloud form sparked similar concerns that aliens were invading earlier this year when a circular cloud formation was spotted on the east coast north of Auckland.

Sheila Russell told RNZ at the time that her initial thought was “Wow, a UFO cloud.”

Ben Noll, a meteorologist with Niwa, put her mind at rest identifying that phenomenon as a “fall streak hole” formed by super-cooled water falling out of clouds and leaving a hole behind.

The lenticular clouds are actually layers of clouds stacked vertically in the atmosphere, but look joined-up when viewed from ground level.

This was the first time King had ever seen anything like this.

“I thought it was amazing,” she said.

“I thought of Star Trek… Beam me up Scotty!”