What were strange 'rainbow clouds' seen above Peterborough?

Residents were given a stunning, colourful sight this afternoon when strange clouds appeared above Peterborough.

The ‘rainbow clouds’ were seen across the city, leaving some to wonder whether they were affects of the aurora borealis – also known as the Northern Lights.

Arora Watch UK said there was no significant activity in the UK from the lights.

On X (formally known as Twitter) Andy Griffin wondered if the clouds were Santa keeping an eye on the city’s children, while Peterborough Cathedral posted that it could be a sign that Mars was arriving early – alluding to the exhibition arriving in the new year.

However, Trevor Robbins-Pratt, from Peterborough Weather Watch, said the strange phenomenon was in fact a group of Nacreous clouds.

According to the Met Office, Nacreous clouds are rare and very high clouds, known mainly for the coloured light they reflect after sunset and before sunrise. The colours are reminiscent of the colours which reflect from a thin layer of oil on top of water, an effect known as iridescence.

They 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.

Due to their high altitude and the curvature of the Earth’s surface, these clouds are lit up by sunlight from below the horizon and reflect it to the ground, shining brightly well before dawn and after dusk. They are most likely to be viewed when the Sun is between 1º and 6º below the horizon and in places with higher latitudes, such as Scandinavia and northern Canada. For this reason, they are sometimes known as polar stratospheric clouds.

Because of the very low temperatures required, nacreous clouds are usually only visible from the UK when the cold air which circulates around polar regions in the stratosphere (known as the stratospheric polar vortex) is displaced and hovers temporarily over the UK.

The cloud’s name is believed to come from the old English word “Nacre” which means “mother of Pearl”