The clouds must be very thin and made of ice crystals or water droplets of uniform size. So cloud iridescence usually happens in lenticular or alto-cumulus, cirrus and cirrocumulus clouds.

Sundogs are formed when light passes through hexagonal plate crystals of ice, suspended in cirrus or cirrostratus clouds located at altitudes of around 20,000 feet (6,000 meters) and higher, up to ...

An unusual atmospheric phenomenon known as a circumhorizontal arc, or "fire rainbow," was spotted in southern Ohio, caused by sunlight refracting through ice crystals in cirrus or cirrostratus clouds.

Observatory shares video, explaining ‘circumhorizontal arc’ is not a true rainbow but optical phenomenon formed by sunlight ...

This occurs when “water droplets or ice crystals in the cloud diffract the light around the outside of the droplet, as opposed to bending the light through it,” according to Weather Channel ...

They occur when the sun's rays interact with ice crystals or water droplets in the high-altitude clouds. That causes the light to diffract and scatter into a spectrum of the colors of the rainbow.

The ice crystals that make up these clouds provide a surface upon which chlorine in the stratosphere can be converted to highly reactive compounds like chlorine monoxide.

An unusual atmospheric phenomenon known as a circumhorizontal arc, or "fire rainbow," was spotted in southern Ohio, caused by sunlight refracting through ice crystals in cirrus or cirrostratus clouds.

An unusual atmospheric phenomenon known as a circumhorizontal arc, or "fire rainbow," was spotted in southern Ohio, caused by sunlight refracting through ice crystals in cirrus or cirrostratus clouds.