Clouds form when invisible water vapor in the air condenses into visible water droplets or ice crystals. This condensation occurs when the air becomes saturated, meaning it cannot hold all the water vapor it contains, causing the excess vapor to change into liquid or solid form
. The process begins with water evaporating from sources like oceans, lakes, and rivers due to heat from the sun. This water vapor rises with warm air. As the air rises, it cools, and cooler air cannot hold as much water vapor as warm air. When the air cools to its dew point—the temperature at which it becomes saturated—water vapor condenses onto tiny particles in the air such as dust, salt, or smoke, called condensation nuclei
. This condensation forms tiny water droplets or ice crystals that cluster together to create clouds. These droplets are extremely small, about 20 micrometers across, allowing them to stay suspended in the air. Clouds remain afloat partly because warm air continues to rise beneath them, pushing them upward, and because the droplets are so small they fall very slowly
. In summary, clouds form through these key steps:
- Water evaporates into water vapor.
- Warm air carrying this vapor rises and cools.
- Cooling air reaches saturation (dew point).
- Water vapor condenses on condensation nuclei into droplets or ice crystals.
- These droplets cluster to form visible clouds suspended by rising air currents
This natural cycle explains why clouds appear in the sky and sometimes at ground level as fog.
