circumzenithal arc over Hull, England
© Lee Middleton
A rare 'upside-down rainbow' has been spotted in the sky above Hull.

Lee Middleton was walking near Swinderby Garth in Bransholme on Tuesday afternoon when his five-year-old son Tyler saw the unusual phenomenon.

He said: "Tyler saw it first and shouted that their was a rainbow in the sky.

"As I looked it blew my mind, the colours are the opposite way round to a rainbow I think - it was so strange, I had never seen anything like it.

"Of course we've all seen rainbows but a rainbow in the sky without rain? Incredible sight."

According to the Met Office, the 'upside-down rainbow' was actually a circumzenithal arc.

They are a type of 'halo', a circular rainbow which forms high in the sky when sunlight refracts through ice crystals in clouds.

They are most commonly associated with cirrus clouds, which are thin, wispy, hair-like clouds that form at high altitudes.

Although these optical phenomena occur quite commonly and can form throughout the year, they are rarely seen because they are often obscured from view by lower-hanging clouds.

A number of conditions must coincide for the circumzenithal arc to be seen clearly, including the height, depth and position of the ice clouds, the angle of the ice particles relative to the sun and the position of the observer.