A rare sight: Why nacreous clouds graced our skies

In recent days we've seen several sightings of nacreous clouds across the UK, a rare right for us indeed. So why have they frequented our skies?

Nacreous clouds, resembling, and subsequently also called mother of pearl, typically develop in the frigid air above polar regions, forming only below -78°C.

They showcase a stunning pastel glow post-sunset and pre-sunrise, created by sunlight diffracting around tiny ice crystals within.

Sightings in the UK are rare and only occur when the cold air associated with the polar vortex, circulating in the stratosphere, is temporarily displaced over the region.

These clouds, reaching heights three times that of cruising airplanes, serve as indicators of exceptionally cold upper atmospheric conditions.

Due to the stringent temperature requirements for their formation, these clouds are usually observed over Scandinavia, northern Canada, and northern Russia. Their last sighting in the UK was in Scotland, nearly one year ago.

Due to the requisite height and temperature, they are also referred to as Polar Stratospheric Clouds, witnessed in regions like Scandinavia and Canada.