‘Rare natural phenomenon’ spotted over Darlington after heatwave

Nicholas Kemp photographed the unusual formations above his street, with the distinctive bubble-like pouches of cloud clearly visible beneath a heavy, brooding sky as the intense heat finally gave way to thundery conditions.

“I’ve never seen them before, but I knew about them,” the 65-year-old former caretaker said.

“It was quite amazing to witness a rare natural phenomenon, especially over Darlington.

“My dad was an amature meteorologist.

“He taught everything about the weather. He never in his 85 years of watching the skies, saw these clouds. They are amazing.”

What are mammatus clouds?

Mammatus clouds, whose name comes from the Latin word mamma, meaning ‘udder’, are one of the most distinctive and unusual cloud formations visible in the UK.

Rather than the typical puffy forms associated with storm clouds, mammatus appear as rounded, pouch-like lobes hanging downwards from the underside of a cloud, most commonly a cumulonimbus thunderstorm cloud.

They form when cool air sinks downwards, creating the characteristic drooping pockets that contrast sharply with the rising columns of warm air driving the storm above. Individual lobes typically measure between one and three kilometres across and can last around ten minutes, though a whole cluster can persist for several hours.

Sightings in the UK are uncommon.

The Met Office describes them as forming under the most unstable cumulonimbus clouds, making them a strong visual signal that heavy rain, hail or a significant thunderstorm is imminent.

They are also of concern to pilots, who are advised to avoid any cumulonimbus cloud displaying mammatus formations due to the severe turbulence they indicate.

End of a record-breaking heatwave

The clouds appeared on Friday, June 26, as high pressure that had driven one of the most intense heatwaves in recent British history began to break down and give way to showers and thunderstorms.

The heatwave had pushed temperatures to potentially record-breaking levels earlier in the week, with the Met Office issuing a red extreme heat warning for parts of southern England and Wales as forecasters predicted highs of up to 39°C — figures that threatened to surpass the UK’s all-time June temperature record of 35.6°C, set in 1976.

The North East, while cooler than southern England, was not spared the oppressive heat and humidity.

Nor was it spared the storm, as video from The Northern Echo office show.

By Friday, the Met Office had forecast that a westerly change would bring cloud, rain and thunderstorms sweeping in from the west, with conditions becoming more unsettled across much of the country through the weekend.

It was precisely these volatile, stormy conditions — warm, unstable air colliding with the incoming cooler westerly flow — that created the perfect conditions for mammatus clouds to develop over Darlington’s skies.