This afternoon I saw a marvellous sight in the sky: a circumzenithal arc. I only noticed it because I was looking at some puffins which passed directly overhead, and that’s where this ‘upside-down rainbow’ was:
These brightly coloured bows are caused by sunlight refracted through ice-crystals high up in the sky. Look closely and you can also see one of the parhelia, on the right side of the sun.
If you are interested in seeing these things yourself, here’s an atmospheric optics website that has a list if the most frequently appearing halos.