High-level clouds

Cirrus clouds.

Cirrus clouds are ice clouds. They can look like delicate white feathers or streamers. They are always more than three miles up where the temperature is below freezing, even in summer. Wind currents twist and spread the ice crystals into wispy strands.

Contrails in the sky.

Contrails are made by high-flying jet airplanes. They are still clouds, though, because they are made of water droplets condensed from the water vapor in the exhaust of the jet engines.