EXTREMELY rare clouds known for their pearly-white appearance, normally limited to the polar regions, appeared over Scotland on Tuesday.

Weather-watchers caught the nacreous clouds, which form at 80,000 to 100,000 feet above the ground, over Edinburgh and Fife.

They require temperatures below -78C to exist, levels of cold which usually only appear in the polar reaches of Canada, Scandinavia and Russia.

Scattering of sunlight around the tiny ice crystals inside the clouds causes their pearly, iridescent appearance.

The clouds also appeared over Staffordshire, Lincolnshire, Merseyside and Cheshire.

READ MORE: Delayed 2035 completion date for dualling A9 ‘very realistic’, insists minister

Viewers were both amazed and confused by the display, with some questioning if they were the Northern Lights.

Other people took a more humorous tack, with one Twitter/X user suggesting its orange oblong shape was a contrail from Santa's sleigh.

READ MORE: UK Government to seek legal expenses over Scotland gender bill row

Meteorologist Jo Farrow explained on Twitter/X why the clouds were so brilliant after sunset, writing: "The usual clouds are dark because the sun has set but the nacreous clouds are so high that they are still receiving the sun's rays, which makes them stand out."

The clouds last appeared over Scotland in January, forming above Aberdeenshire, Moray and the Highlands.

The Met Office describes some of the clouds' unique characteristics on its website, saying: "Nacreous clouds form in the lower stratosphere over polar regions when the sun is just below the horizon.

"The ice particles that form nacreous clouds are much smaller than those that form more common clouds.

"These smaller particles scatter light in a different way, which is what creates the distinctive luminescent appearance."