According to Met Office, clouds form when water vapor in the air condenses into tiny drops of water or ice crystals that then settle on dust particles in the atmosphere. Condensation happens when the air is saturated and cannot hold any more water vapor; this can occur when the amount of water in the air increases or when the air is cooled to its dew point.
According to Met Office, there are five factors that lead to the formation of clouds. Surface heating is when the ground is heated by the sun; the air in contact with the ground is then also heated and begins to rise, producing cumulus clouds. The topography of a region can cause the formation of clouds when air is forced to rise over hills or mountains and cools. Fronts, boundaries between warm air and cool air, cause cloud formation when a mass of warm air rises up over a mass of cold, dense air. The convergence of streams of air flowing from different directions and being forced to rise cause cumulus clouds to form. Finally, turbulence created by a sudden change in wind speed can form clouds. Because of the many ways in which clouds can form, there are a variety of cloud types of different shapes, sizes and textures.