Why does the beach wind flip between day and night?

In the afternoon the wind blows in off the water, cool on your face. Come back at night and it's blowing the other way β€” out toward the sea. Nothing tells it to turn around. So what keeps flipping the coast wind?

1Two things to know about air and heat

Hot air rises β€” and land and water soak up sun differently

You only need these two ideas. Watch each one:

Hot air floats up, cool air slides in

Warm air is lighter, so it rises. Cooler, heavier air rushes in underneath to take its place. That sliding-in air is what we feel as wind.

Land heats fast, water heats slow

Same sun on both. The sand gets hot quickly. The water barely warms up β€” it needs way more sun to change even a little.

2The two players

Fast-changing land vs slow-and-steady sea

Give them the same sun all day and all night. Their temperatures behave in totally different ways:

The land

Heats fast, cools fast

By afternoon it's baking hot. By the middle of the night it's gone cold. It swings up and down a lot.

The sea

Slow and steady

It hardly changes at all. Warm-ish in the day, warm-ish at night β€” it stays close to the same temperature.

3Your turn β€” shine the sun

Turn up the sun and watch which side heats up

Drag the sun brighter. Watch the land heat up fast while the sea barely budges β€” and watch the air above the hotter side start to rise.

Land
cool
Sea
cool
DIMBLAZING

4The big test β€” push time from day to night

Run a whole day and night, and watch the breeze 🧭

Now you control time, not the sun. Tap forward through morning, noon, evening, and deep night. But first, one guess.

Guess before you run the day

Why does the coast breeze blow inland by day but out to sea at night?