Fire rainbow over Wicken Fen, Cambridgeshire
© Glynis Pierson/National TrustThe rare phenomenon captured at Wicken Fen is also known as a ‘sun dog’ or ‘fire rainbow’ .
These amazing photos show a vivid upside-down rainbow above skies at Cambridgeshire's Wicken Fen nature reserve.

The phenomenon, called a circumzenithal arc, is caused by ice crystals refracting the sun's rays.

The rare turn in weather is also known as a 'sun dog' or 'fire rainbow' - and was captured at Wicken Fen by National Trust volunteer Glynis Pierson.

Unlike normal rainbows, which form when light shines through rain, circumzenithal arcs are likely to appear on clear, still days.

Light hits the ice crystals, held in wispy cirrus clouds, and creates multi-coloured brushstrokes in the sky.
Fire rainbow over Wicken Fen, Cambridgeshire
© Glynis Pierson/National Trust
The natural phenomenon only occurs when the sun is more than five and less than 32 degrees above the horizon.

Howard Cooper, a member of the Wicken Fen visitor experience team, told the News : "The photos were taken by one of our volunteers, Glynis Pierson.

"They have gone down a storm on social media and that's been brilliant to see.

"You don't see something like that every day - people have really been enjoying it."