Why Does the Wind Blow?

Wind — Elementary

The short answer

The main cause of wind is temperature.

That means heat and cold.

Some places are warm. Some places are cold.

That difference is what makes the wind blow.

The Sun does not warm all places the same

The Sun warms up the air.

But it does not warm all places the same way.

The Sun hits different parts of Earth at different angles.

Earth also has oceans and mountains.

So some places get warmer than others.

That makes pockets of warm air and pockets of cold air.

A pocket is like one patch of air in one place.

Warm air goes up. Cold air goes down.

Air is made of gases.

When gases warm up, they spread out.

Warm gases rise. They go up.

You can see this with steam.

Steam comes off a pot of hot water. It always goes up.

When air is cold, the gases get slower.

They move closer together.

Cold air sinks. It goes down.

Crowded air and spread-out air

Warm air and cold air make two kinds of pockets.

One kind is called high pressure.

In high pressure, the gases are more crowded together.

One kind is called low pressure.

In low pressure, the gases are more spread out.

Here is a surprise.

Warm air rises up.

So it leaves low pressure behind it, where it used to be.

Now the wind happens

Gases move from high pressure to low pressure.

Air rushes from the crowded place to the spread-out place.

That rush of air is the wind.

The bigger the difference between the two pockets, the faster the air moves.

A small difference makes slow air.

A big difference makes fast air.

Why does the air move at all?

Things in nature try to even out.

That is called diffusion.

People do it too.

When people get on a bus, they do not all sit on one side.

They spread out, if there are open seats.

Air spreads out in the same kind of way.

Next time you feel the wind, think about this.

Think about where the air is going.

Think about the warm and cold pockets that made it move.

Wind — Middle

The short answer

Wind is a part of weather we experience all the time.

The main cause of wind is a little surprising. It is actually temperature.

More specifically, it is differences in temperature between different areas.

How temperature differences make wind

The gases that make up our atmosphere do interesting things as the temperatures change.

When gases warm up, the atoms and molecules move faster, spread out, and rise.

That is why steam coming off a pot of boiling water always goes upward.

When air is colder, the gases get slower and closer together. Colder air sinks.

The Sun warms up the air, but it does so unevenly.

The Sun hits different parts of the Earth at different angles.

Earth also has oceans, mountains, and other features.

Because of this, some places are warmer than others.

We get pockets of warm air and pockets of cold air.

Different temperatures lead to different pressures

Since gases behave differently at different temperatures, you also get pockets with high pressure and pockets with low pressure.

In areas of high pressure, the gases in the air are more crowded.

In low pressure zones, the gases are a little more spread out.

You might think that warm air would lead to a higher pressure area, but actually the opposite is true.

Because warm air rises, it leaves behind an area of low pressure behind it.

Where the wind happens

Gases move from high-pressure areas to low-pressure areas.

And the bigger the difference between the pressures, the faster the air will move from the high to the low pressure.

That rush of air is the wind we experience.

But why does the air move at all?

You might wonder why the air would move from high pressure to low pressure in the first place.

This is something that happens in nature all the time: things always try to even out.

It is called diffusion.

Even people do it. When people get onto a bus, they do not all sit on the same side of the bus first.

Strangers do not sit next to each other when there are plenty of open seats. People want to spread out as much as possible.

Next time you feel the wind blow, think about where it is going, and what temperatures and pressures are causing it to do that.