The beauty of the cloudy sky

It is a phenomenon that is as beautiful as it is eerie. On Wednesday night, people living in Novosibirsk were treated to the majestic sight of rare mammatus clouds in the sky.

Shaped like udders, or little pouches, hanging from the sky they are normally associated with warm tropical weather and signify the proximity of severe thunderstorms.

Their distinctive puffy patterns give them an almost extra-terrestrial feel and many people who took pictures of the phenomenon joked that they thought the world was ending.

Dozens of pictures appeared online amid a wave of excitement on social media. Among those who posted images was Alexander Kazartsev described seeing a 'green light' illuminating the street while Daria Zykova said his son came to him and described 'snowballs in the sky'. Ekaterina Shalanova wrote: 'The sky was gorgeous!'

Another resident, Valentina Govorukhina, said: 'It was a fantastic view. I was just walking for two hours watching the skies, and did not want to go home.'

Sitting in her room, Katya Slonova posted: 'Terrified, I thought that was the end of the world. I regret that I did not come out into the street to look at those clouds!'

Each individual mammatus puff measures between one and three kilometres in diameter, and can last an average of 10 minutes before dissipating. However, as a cluster – as they were in Novosibirsk on Wednesday night – they can last for a number of hours.

The clouds are normally composed of ice but can also contain water and while they may look foreboding and sinister they simply appear around the time of approaching severe weather storms.