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Unusual 'rainbow' clouds spotted in the south east

17th June 2019 Last updated at 13:49

These striking rainbow coloured clouds, seen by BBC Weather Watchers, had us scratching our heads. We originally identified them as iridescent clouds but after more research we believe they are actually circumhorizon - or circumhorizontal - arcs. It's easy to confuse the two.

As the name may suggest, a circumhorizon arc sits parallel to the horizon. The sun must be higher than 50 degrees in a sky where there is also cirrus cloud. The ice crystals within the cirrus cloud must also be positioned in such a way that allows for the refraction of sunlight, leading to the rainbow colours that appear.

Circumhorizon arcs in the UK are quite unusual. The sun is only more than 50 degrees higher in the sky from May to July so there's a shorter window to observe them. Those who have been able to spot it are very lucky indeed!

Rainbow cloud in the sky
Trevor's weather/Weather Watchers
Trevor captured a colourful spectacle from his back garden in Weybridge, Surrey
Rainbow cloud in the sky
JoMax/Weather Watchers
Pastel hues were seen in Barons Court, London
Rainbow cloud in the sky
Skyspotter/Weather Watchers
Skyspotter photographed a rainbow cloud as it appeared over Tooting, London
Rainbow cloud in the sky
Jen/Weather Watchers
A terrific turquoise cloud in Farnham, Surrey, was photographed by Jen
Rainbow cloud in the sky
CharlieBenSaid/Weather Watchers
CharlieBenSaid snapped the wispy rainbow colours in London
Rainbow cloud in the sky
Eddie the weather/Weather Watchers
A glimmer of colour in the skies above Bishopsbourne, Kent
Rainbow cloud in the sky
Mandi/Weather Watchers
Mandi spotted a pretty display in Guildford, Surrey
Rainbow cloud in the sky
Snow beam/Weather Watchers
This unusual effect appeared in Loose, Kent
Rainbow cloud in the sky
Grant in Streatham/Weather Watchers
Grant says the cloud looked "like an angel wing" when he saw it in Mitcham, London