You can see this with a garden hose -- If you squirt out the water in the air in a strong stream, it hits the ground pretty fast. But if you spray a fine mist into the air, notice how slow the little droplets appear to float and only drift downward. The clouds work the same way, the air currents keep them floating above the ground.
Now, it's when these water droplets get larger and larger that they become heavier than the air currents can support, and they fall to the ground as rain.
The size of the raindrops can tell you how strong the air currents are above the ground. Around here, our rain is pretty light most of the time, but when you get those quick thunderstorms with huge drops, that means the air currents are very strong because they can hold up the rain until it grows to that large size.
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