Why does fog roll over hills?

A true how-it-works story for kids 6-8.

Watercolor illustration for Why Fog Rolls Over Hills

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Look out! Is a cloud crawling over that hill? Fog is a cloud close to the ground. And those rolling waves have a windy helper! Fog is made of tiny water drops.

They are so small that they can hang in the air. Hello, fog! Wind pushes fog from the ocean toward land. When the moving air meets a hill, it can flow up and over, carrying the tiny drops along. Whoosh!

It looks like a blanket being pulled over a sleeping giant. Someone forgot to tuck in the giant's toes! From your seat, look for a hilltop appearing or disappearing. Can you spot which way the wind is moving the fog?

Quiz the back seat

What carries ocean fog over hills?

Show the answer

Wind. Wind! Fog's water drops are so tiny that they can hang in the air.

3 fun facts

Fog is a cloud close to the ground made of tiny water droplets or ice crystals.
Wind pushes fog from the ocean toward land.
Wind and the shape of the land influence how fog moves.

Questions kids ask

Why does fog roll over hills?: Wind can carry fog up and over hills as the moving air flows across the land.
How does ocean fog form?: Moist air cools over cold ocean water, turning some invisible water vapor into tiny drops.
Is fog a cloud?: Fog is a cloud close to the ground.

For grown-ups

Written with AI from public sources, then checked claim by claim against the sources below before it was published; stories that don't pass stay off the app and this site. Narration is pre-recorded, and nothing you do on this page is tied to your kids.