- A photographer captured the rare phenomenon in the skies above Newcastle, Country Durham and Northumberland
- It is caused by tiny ice crystals that form clouds in the mesopause and scatter the twilight from the summer sun
- Noctilucent clouds are normally only visible in the weeks around summer solstice in more northerly latitudes
Pictures captured in northern England show the midnight skies illuminated with an electric blue colour.
The phenomenon was caused by rare noctilucent clouds - extremely small ice crystals that form in the mesopause - that sit more than 47 miles (75km) above the Earth's surface.
These clouds, which are the highest in the Earth's atmosphere, scatter the sunlight as it dips low in the sky, creating an eerie glow.
They usually occur in the weeks around the summer solstice when sunlight dips just below the horizon to illuminate the clouds.
And noctilucent clouds are normally only seen in more northerly latitudes towards the polar regions.
However they are thought to be becoming more frequent at lower latitudes and some blame crowing concentrations of greenhouse gases are causing the mesopause to grow colder in the summer.
Photographer Paul Kingston, 33, from County Durham, captured the noctilucent clouds at around midnight on Tuesday.
The phenomenon is rarely seen in lower latitudes and only occurs around the summer solstice when temperatures in the mesopause drop. The image above shows the vivid blue glow in the sky above the roofs of houses in Barnard Castle in Country Durham.
Noctilucent clouds lit up the skies above Heddon-on-the-Wall in Northumberland (above) with vivid silver and blue light close to midnight.
Mr Kingston said: 'I was taking one last look outside before going to bed, which I often do to gauge the weather, and saw the lights on the horizon.
'I took a drive out and shot these pictures. It was an amazing sight, and strange to see the sky lit up in such vivid colour right in the deaf of the night.'
Noctilucent, or 'night shining', clouds are often photographed from aircraft in flight or from space station, when they are known as Polar Mesospheric Clouds.
The blue light is caused by summer sunlight hitting the ice in noctilucent clouds that form around 50 miles up in the Earth's atmosphere. They are thought to form when the temperature of the mesopause falls below -123°C (-189°F), which tends to only occur during a few weeks around the summer solstice when global circulation in the middle atmosphere causes these temperatures.
However, the source of the water vapour that forms the ice is now known as the mesosphere is extremely dry. It is thought it may be carried upwards by currents although rocket exhausts have also been linked to the effect.
The crystals are thought to form around dust thrown high into the atmosphere from volcanoes and some scientists have also suggested dust from meteors may also play a role.
The noctilucent clouds turned the sky a vivid blue on Tuesday night, as shown in the image above looking over the city of Newcastle.
Comment: Noctilucent clouds were also captured a couple of days ago near Minsk, Belarus: