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ELI5 Yahaaa

The sky letting go

Where Does Rain Come From?

Rain is water that rose invisibly, gathered into drops, and got too heavy to stay up.

1 Water rises asinvisiblevapour2 It cools intotiny droplets3 Droplets mergeand fall
Every raindrop was once part of the sea.

  1. Step 1 of 5

    Water leaves the ground without you seeing it.

    Warm water Invisible vapourrising

    Sun warms oceans, puddles and leaves, and water escapes as vapour — a gas so thin it is completely invisible.

  2. Step 2 of 5

    Rising air gets colder.

    Ground levelwarm — holdslots of vapourHalfway upcooler — holdslessCloud heightcold — holdsalmost none

    Higher up, the air is thinner and much colder. Cold air cannot hold as much vapour, so the vapour has to turn back into liquid.

  3. Step 3 of 5

    A cloud is billions of tiny droplets.

    A cloud from below Millions of droplets,each smaller than ahair's width

    Each droplet forms around a speck of dust or salt. They are so small and light that they float — which is why clouds do not fall.

  4. Step 4 of 5

    Droplets bump and merge.

    1 Tiny droplets2 They collideand merge3 One raindrop, amilliondroplets' worth

    Inside the cloud, droplets collide and stick. A raindrop needs about a million cloud droplets to combine before it is big enough.

  5. Step 5 of 5

    Gravity wins, and it rains.

    A growing dropRising air holds it upGravity pulls it down

    Once a drop is heavy enough that rising air cannot hold it, it falls. Darker clouds simply hold more water, which is why they look grey.

    A raindrop is not tear-shaped. Falling flattens it into something more like a tiny burger bun.

The short version

Rain is evaporated water that cooled into droplets, merged until heavy, and fell.

Try it yourself

Breathe onto a cold window. Your invisible breath vapour cools and becomes visible drops — a cloud and rain in one second.

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