Nacreous clouds, which are only rarely seen outside the far north, have been seen by hundreds of people above Co. Antrim and elsewhere throughout Ireland.
By The Newsroom
Published 2nd Feb 2016, 11:36 BST
Updated 2nd Feb 2016, 11:40 BST
They are filmy sheets slowly curling and uncurling, stretching and contracting in the semi-dark sky at dawn.
Such clouds are more common in Scandanavia, Iceland, Alaska and Northern Canada, with rare sightings in Ireland.