An unusual upside down rainbow was spotted over Swansea on Thursday night. The multi-coloured arc left residents across the city confused as it appeared in the shape of a ‘U’ rather than, well a rainbow shape! People reported seeing it from Birchgrove, Fforestfach, Sketty, Clydach and even Rotherslade. How did it occur? According to the Met Office , the upside down rainbow is actually a circumzenithal arc. The upside down rainbows appear when the sunlight refracts through ice crystals in cirrus clouds. This type of rainbow is quite common but we usually can’t see them because of the clouds underneath.
Source: Upside down rainbow spotted in skies of southern Wales