云是从哪来的

Clouds form when sunlight and heat from the sun warm the air, causing it to rise and cool, condensing into water droplets or ice crystals. There are three main types: convection, or rising air near the Earth"s surface; advection along coastal slopes; and the meeting of cold and warm air masses. Although clouds and fog are similar, they differ in their ability to produce rain, snow, lightning, and fog only affects visibility.