One of the highest clouds in our atmosphere, they are often called “mother-of-pearl”, because of the beautiful colours – they are rarely spotted in the UK because of the exceptional conditions needed.
The phenomenon is nacreous clouds. They are between 12 and 20 miles high.
According to weather experts, freezing cold polar air, locked in place by high winds in the upper atmosphere, known as the polar vortex – weakens and allows this colder air to sink south to our latitude.
Made in air that is around -80˚C, very small ice crystals refract the sunlight, giving the cloud its rainbow colours.
Nacreous clouds are mostly seen a couple of hours either side of sunset or sunrise and, being so high, they are still lit by sunlight which makes them appear even brighter in our evening sky.
Because of the height and temperature needed this cloud is also known as Polar Stratospheric Cloud.
