It was an unusually cold, Saturday morning, at -4C, when a woman was walking her dog on the fields around the village of Tremeirchion, Wales. However, she could not believe her eyes at what she saw: a strange, hovering dome.

Hannah Blandford, 33, immediately took shots of the weird object.

"I'd never seen anything like it before, it was really quite special," she said, amazed.

Could it be a UFO? Or was it just a weather phenomenon? This was just one of the many UFO sightings that have been reported by HNGN this year. Yet this one seemed "special."

Hannah Blandford added: "I couldn't believe how perfectly dome-shaped it was, it looked amazing, so I had to take a photo. I'd never seen anything like it before, it was really quite special. I watched it for about 10 minutes and then the dome started to flatten and it looked like very thick, low-lying cloud. It spread out across 12 fields and covered a huge area."

By putting up the post on Twitter, she started her own UFO streak in social media.

A number of users explained that it could be a "cloaking device" for an alien spaceship. Many other users said that it was an "attack" by aliens on Wales!

"UFO camouflaged!" cried one reader.

Another wrote: "Aliens nods".

The most 'reasonable' forecast was made by Met Office forecaster John West. He explained that the fog dome had probably been made by some heat generated from the ground.

He said: "This is a very unusual phenomenon, but the most likely explanation is that the fog dome has been caused by a source of heat close to the ground, possibly an agricultural building or a relatively warm pool of water.

"As the fog has formed in the valley this heat source has forced the fog to lift away from the ground into a dome as warmer air rises, like a hot air balloon."