How clouds form
A cloud is a crowd of water droplets or ice crystals so small that they float in the air. For one to appear, three ingredients are needed: water vapour, cooling and suspended particles.
Warm air near the ground rises because it is less dense than the cold air around it. As it rises it expands and cools. At some height the vapour condenses on grains of dust or salt, and millions of those droplets together form the visible cloud.