Ever See These Beautiful Clouds Overhead?

Like brushtrokes in the sky, mare's tail clouds are thin, wispy streaks high in the sky that resemble the flowing tail of a horse.

They’re a type of cirrus cloud, forming above 20,000 feet where temperatures are far below freezing. Instead of water droplets, these clouds are made of ice crystals that are stretched into long, feathery shapes by strong winds high in the atmosphere, often near the jet stream.

These clouds also carry a long history in weather folklore. The old saying, “Mares’ tails and mackerel scales make lofty ships carry low sails,” reflects the idea that when these clouds appear, stronger winds and unsettled weather may be on the way.

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In modern terms, mares' tails can signal increasing winds aloft and an approaching weather system. Because they mark areas of fast-moving air, they’re sometimes associated with turbulence, offering a subtle but meaningful clue that changes may be brewing overhead.

Jennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.