A number of conditions are required for cloud formation. Chief among them are the presence of moisture, lift and nucleating surfaces. When the sun shines on water bodies, it heats the water and causes it to evaporate (the conversion from liquid water to water vapor). These water vapors need to be lifted high enough into the atmosphere for cloud formation. This lift may be provided by fronts associated with low pressure systems, convection, convergence, etc. As the air rises, it cools. Once it reaches the condensation level, water starts condensing. To nucleate, water vapors need solid surfaces. These surfaces could be something as simple as dust blown by wind and are known as cloud condensation nuclei. The nucleated water drops form larger droplets and fall down in the form of precipitation.
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