Rain and Wind

Lush New England vegetation under a July sun transpires an immense amount of water as invisible vapor that wafts along the warming ground and rises whenever other, often drier, air can slip into its former place. The rising, moist air ascends thousands of feet before the conveyor belt of vapor cools to its dew point and begins to form billions of tiny points of water.
These bits of water swirl and mix and bump into each other as the air rises further. At some particular height, enough droplets form to become visible as a flat-bottomed cloud that reveals much as its upper folds and billows give contour and motion to the air and its growing burden.
Soon, as the droplets stick to each other, they grow heavier than the rising air can carry further, and aggregate so thickly that they block the sun and give the darkening clouds an ominous look. Then they fall.
No longer vapor, the physical drops must push down through the air, each substantial drop displacing an equal amount of air as it falls. By the countless billions, the avalanche of drops overwhelms the air, driving it before it in great downwelling gusts that render the cloud bottoms and herald the imminent rain. Soon, a deluge strikes the earth, the blow bending blade and bough, which droop heavily under the pelting rain that quenches the thirsty soils from which it came but a few hours earlier.