The noctilucent cloud season has started. Each summer these stunning clouds can appear at night glowing in silvery-blue threads, slowly rippling across the sky. The clouds were photographed by Andy Stables on the Isle of Skye on May 28, and can be seen at on.fb.me/1K93EPK. The clouds will gradually appear across the UK, usually reaching a peak around three weeks after the summer solstice.
Noctilucent clouds are like no other clouds on Earth. They are the highest in the world, close to the edge of space at around 80km (50 miles) high, in the layer of upper atmosphere called the mesosphere. They appear at twilight some 30 to 60 minutes after sunset, when the last rays of the Sun hidden under the horizon beam