READERS have been sending in their photographs of an atmospheric phenomenon rarely glimpsed in England but which appeared in the skies above East Lancashire last night.

Nacreous clouds form in the stratosphere between 49,000 to 82,000 feet during polar winters, when the when the temperature drops below -78 degrees Celsius.

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Due to their high altitude the clouds receive sunlight from beneath the horizon and reflect it to the ground.

They are usually only seen during winter at high latitudes in places such as Scandinavia, Iceland, Alaska and Northern Canada, but can sometimes be seen in England at twilight, when the sun is between one and six degrees below the horizon.

Scattering of radiation within the clouds give them their pearly white appearance and nickname – mother of pearl – while particles within the clouds are diffracted, leading to their rainbow colouration.

The effect can produce vivid and bright colours against an otherwise darkening sky and is often mistaken for the aurora borealis or northern lights.