This is Mr. Water Drop:

Mr. Water Drop freezes at 32 degree Fahrenheit.  When Mr. Water Drop is Way Up in the Sky, where it is very cold, he and billions of his friends freeze into tiny crystals to form Mr. Cloud.

You may wonder where Mr. Water Drop comes from. Well, I will tell you.
Sometimes Mr. Water Drop evaporates from the Big Ocean and becomes an invisible gas for a while, till he floats up and then cools down Way High Up in the Sky Where it is Cold and becomes either ice crystals who make up Mr. Cloud, or else liquid that makes up Mr. Rain.
But there is another, more wonderful place that Mr. Water Drop comes from: Mr. Fire!

Does that surprise you?
It’s true. When Mr. Fire burns things made out of carbon and hydrogen (like the wax in that candle), then oxygen in the air combines with those two elements to make a gas called “carbon dioxide” that plants think is yummy. But it also makes another gas called “H2O”. And guess what H2O is also called? That’s right! Mr. Water Drop!
Now here’s a funny thing: When Great Big Jet Airplanes fly Way Up High in the Sky, they have to burn something called “jet fuel”. Jet fuel is made of carbon and hydrogen too, which burns very well. It’s like the gasoline mommy and daddy put in your car!  And when the jet fuel burns, it gets blasted out of the jet engines to push the plane along through the sky! Here is a pretty plane full of nice people flying through the sky:

Do you notice something funny about that plane? That’s right! It’s making two lines of clouds! Want to know why? Because it’s Way Up High the Sky where the air is colder than 32 degrees! So