What cirrus clouds look like
Most of the time, you see cirrus clouds very high up in the sky, looking thin and wispy, like someone pulled a bigger cloud apart into little bits of cloud.
Why do cirrus clouds look wispy?
Cirrus (SIR-russ) clouds look thin because they are made of ice crystals, not water drops. They form where it is high enough to be cold. The higher you go above the earth, the nearer you are to space, and the colder the air is. That cold air can freeze water drops into ice.
Cirrus cloud or airplane trail?
Sometimes you might think you see cirrus clouds when it’s really only the trail of an airplane, half blown away and spreading across the sky. Those airplane trails are called contrails. That’s short for “condensation trails”.
Contrails form when the hot air shooting out of the airplane’s engines hits the cold, thin air of the upper atmosphere. The hot air holds water, but cold air can’t hold as much water as hot air. So as the hot air cools down suddenly, the water freezes out of it and forms thin clouds made of ice crystals – the same as cirrus clouds.
But either way, if the sky is blue with only these thin cirrus clouds high up in it, you can be pretty sure it’s going to be a nice day.
Learn by doing: go outside and try to identify the different clouds you see
More about clouds