Clouds appear to float in the sky, defying gravity. They are made of countless tiny water droplets and ice crystals. These particles are so small and light that they can remain suspended in the atmosphere. The key to understanding why clouds don't fall lies in the balance between gravity and air resistance.
The key difference between cloud droplets and raindrops is their size. Cloud droplets are incredibly tiny, only 10 to 20 micrometers in diameter. This is about 100 times smaller than raindrops. Because they are so small, the gravitational force acting on them is very weak, while air resistance becomes relatively much stronger. This creates a balance that keeps the droplets suspended in the air.
Cloud droplets quickly reach their terminal velocity, which is only about 1 centimeter per second. At this slow speed, the downward gravitational force is perfectly balanced by upward air resistance. Meanwhile, air currents in the atmosphere, called updrafts, can easily overcome this small downward velocity and keep the droplets suspended or even lift them to higher altitudes.
Clouds do eventually fall, but only when the droplets grow large enough. Through a process called collision and coalescence, tiny cloud droplets bump into each other and merge together. As they grow larger and heavier, gravity eventually overcomes air resistance, and they fall to the ground as raindrops. This is how rain is formed from clouds.