Bizarre cloud formation appears over southern California

'I knew it didn't look right,' one man said about the strange disc-shaped holes. Photo / USAPatriotAK47 YouTube

UFO enthusiasts believe a mysterious pattern that appeared in the sky over southern California are proof aliens are watching the Earth.

The eerie images show a pattern of strange disc-shapes emerging in the clouds above Temecula, about halfway between Los Angeles and San Diego.

The bizarre spectacle was filmed and posted on YouTube by USAPatriotAK47, and viewed more than 26,000 times.

A bizarre pattern appeared in the sky over southern California this week, some people thinking it could be aliens. Photo / USAPatriotAK47 YouTube

"Wow I saw this driving on the way to work on the 15 freeway in Temecula and I knew it didn't look right," commented Joesef Hernandez.

According to The Sun, some users speculated it's where an alien spacecraft "decloaked", akin to starships in sci-fi movies like Star Wars and Star Trek.

"You can see a contrail right next to it," wrote Javier Rivera.

Others weren't so sure.

"This is not a UFO, this is the haarp weapon. Haarp means weather control," one user wrote, referring to a theory about a secret US government weapon that can manipulate the atmosphere.

Some believe it can disable satellites and even control minds.

It's not the first possible UFO sighting this year, and some have been closer to home.

Earlier this year, Kiwis in the South Island reported seeing a bright ball of fire, with a tail, flying across the skies. However, it was most likely debris from cargo sent up to the International Space Station.

In January, strange lights appeared on the horizon near Darwin. The phenomenon was captured on dashcam at a service station. Just six months later, Airport workers at Miami airport spotted something that looked like a UFO.