The tiny drops of water have a radius as small as 0.001cm and their terminal velocity when they fall through the air of coefficient of viscosity \( \eta=0.00018 \) is about 1.2 cm/sec. So they remain suspended in the air and float as clouds.

On the other hand, the bigger raindrops have a radius of about 10 times greater (i.e,. 0.01 cm) and their terminal velocity is about 120 cm/sec. So they fall through the air instead of floating in the air.