Striking displays of clouds which are mostly only seen in the summer months have been appearing in the skies over Northern Ireland in recent nights.
Noctilucent clouds occur at extremely high levels in what is known as the mesosphere – a layer in the atmosphere above where our regular clouds and weather systems live, about 76-85km high – on the edge of space.
The clouds require very low temperatures in this part of the upper atmosphere, which only happen in the summer months, to allow water vapor to freeze into ice crystals.
These ice crystals then need to condense onto dust particles, which can originate from meteors or even volcanic eruptions.
Noctilucent clouds, also known as night-shining clouds, become visible when the sunlight, even though the sun is below the horizon, illuminates them from below, creating a shimmering effect.
According to the Met Office, the best time to see noctilucent clouds is on clear nights between late May and mid-August, about 90 to 120 minutes after sunset or before sunrise.
Sightings are most common during June and July.
