Bright, shimmering noctilucent clouds illuminate the skies each year, with a season spanning from June to August.

Known as noctilucent clouds, these rare clouds form around 50 miles above Earth's surface in the mesosphere during summer months.

The unusual display of blue and silver ribbon clouds can keep the evening sky bright hours after the Sun has set, this weekend they appeared over parts of Europe.

It is not known for sure how these clouds form, although we know that they shine thanks to the Sun's light illuminating ice crystals from beyond the horizon.

These crystals reflect the light onto dust particles in the mesosphere, where temperatures reach -134°C.

Best viewed when the Sun has just set below the horizon, 90 minutes after sunset, the clouds are most likely to appear between June and August for those of us in the Northern Hemisphere.