NSES Content Standard D 
Earth and Space Science: Structure of the Earth system
Grades 5-8, page 160

Clouds, formed by the condensation of water vapor, affect weather and climate.

Benchmark 4B The Physical Setting: The Earth
Grades 3-5, page 68
When liquid water disappears, it turns into a gas (vapor) in the air and can reappear as a liquid when cooled, or as a solid if cooled below the freezing point of water. Clouds and fog are made of tiny droplets of water.