Clouds are made of tiny drops of water or ice crystals that settle on dust particles in the atmosphere. The droplets are so small - a diameter of about a hundredth of a millimetre - that each cubic metre of air will contain 100 million droplets. Clouds will either be composed of ice or water droplets depending on the height of the cloud and the temperature of the atmosphere. Because the droplets are so small, they can remain in liquid form in temperatures as low as -30 °C. Extremely high clouds at temperatures below -30 °C are composed of ice crystals. How do clouds form? Clouds form when the invisible water vapour in the air condenses into visible water droplets or ice crystals. There is water around us all the time in the form of tiny gas particles, also known as water vapour. There are also tiny particles floating around in the air - such as salt and dust - these are called aerosols.
clouds are formed when water vapor rises in the atmosphere and condenses onto very small particles like dust,dirt and sea water. when sun heats the river,seas ponds ,lakes and all the water bodies water gets evaporated and forms vapor and then slowly-slowly a large amount of water is collected and when clouds burst we can see it in the form of raining .
               i hope that this will help u.............^_^
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