This is a Fire Rainbow, one of the rarest weather phenomenon on Earth. In order for this effect to be achieved the clouds have to be Cirrus and 2kms high, and there must be a sufficient density of ice crystals in the air in order to refract and reflect the sunlight. The crystals need to be fairly large and plate-shaped. The sunlight then needs to strike the crystals at exactly 58 degrees, and voila! One of the most beautiful things I’ve never seen. This gorgeous optical phenomenon is also known as a Circumhorizontal arc or ice-halo. Variations of the phenomenon include the Infralateral arc and the Supralateral arc.