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WEATHER U: Curious about colourful clouds

Terra Michelle looked up and saw pretty pastels in the clouds over Robert Kemp Turner School in Cole Harbour. N.S.  She says, " they were too beautiful not to share"!
Terra Michelle looked up and saw pretty pastels in the clouds over Robert Kemp Turner School in Cole Harbour. N.S. She says,

They are often bright white; they can be grey or even quite dark. But how about pastel-shaded clouds?

I didn’t see them, but many did. I received more than half a dozen photos of an optical phenomenon known as “cloud iridescence.” 

Cloud iridescence is a fairly rare phenomenon usually seen in altocumulus or high cirrus-type clouds. The colours in the cloud are similar to those seen in soap bubbles or oil on the road after a rain. The lovely display can also be described as cloud irisation; that term comes from Iris, the Greek personification of the rainbow. 

Here’s what happens:

When parts of clouds are thin and have similar-sized droplets, diffraction can make them shine with stunning colours. These colours are usually found in random patches or bands. Iridescence is usually seen in the edge of a cloud that is forming; that’s where the droplets will have a similar history and therefore a similar size. 

Because these pretty pastel patches are usually found in the vicinity of the sun, they’re often hard to see. It’s never a good idea to stare directly into the sun, so the best way to see an iridescent cloud is to place the sun behind a foreground object, like a building or a large tree.

Look up, but always remember to protect your eyes! 



Cindy Day is the chief meteorologist for SaltWire Network.

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