Flying horses

These pretty, wispy clouds are a type of cirrus cloud known as cirrus uncinus. The name is derived from Latin and means "curly hooks". The clouds occur at very high altitudes, at a temperature of about −50 to −40C. They are commonly known as mares' tails because of their likeness to horse tails. 
Given the current state of the world we might be forgiven for thinking 
 that the Four Horsemen of the Apocalypse are on the loose!