The moon’s appearance is a rich source of weather lore: When the muin is on her back, Mend yer shuin and sort yer thack! (Traditional). The famous reference to the moon and approaching storm is in the Ballad of Sir Patrick Spens:
I saw the new muin late yestreen
Wi the auld muin in her airm
And if we gang tae sea maister
I fear we’ll come tae hairm.