These are noctilucent clouds, a rare and beautiful phenomenon that occurs at extremely high altitudes in the mesosphere, which is the layer of atmosphere located about 76 to 85 kilometres above the Earth’s surface. This region lies far above where normal weather and clouds form, placing these clouds close to the edge of space.

Noctilucent clouds require very low temperatures to form in this upper atmosphere layer, conditions that only occur during the summer months. When temperatures drop sufficiently, water vapour freezes into tiny ice crystals.

For these ice crystals to form, they must condense around microscopic dust particles suspended in the atmosphere. These particles often come from meteors burning up as they enter the Earth’s atmosphere or from volcanic eruptions releasing fine dust into the air.

These clouds, also known as night-shining clouds, become visible after sunset when the sun is below the horizon but still illuminates them from below. This sunlight causes the clouds to glow with a shimmering, ethereal light that contrasts beautifully against the darker sky.

According to the Met Office, the ideal time to spot noctilucent clouds is on clear nights between late May and mid-August, roughly 90 to 120 minutes after sunset or just before sunrise.

Sightings are most frequent during June and July. Recently, this rare cloud formation was observed over Portrush in County Antrim, captivating sky-watchers with its lilac and lavender hues glowing softly against the twilight.