Why is it less windy behind a building?

Have you ever stood outside on a windy day? The wind tugs at your coat. It blows your hair across your face and feels cool and pushy on your cheeks.

Then you step behind a big building, and the air goes still. Your hair settles down again. So why is it less windy behind a building?

Wind is air on the move. You cannot see air, but you feel it rush past you. Moving air pushes on everything in its way, like trees, flags and you.

Now the wind races toward a big building. The air bumps right into the wall. The wall is strong and solid, so the air cannot get through. Where do you think the air goes next?

The air slips around the building instead. Some of it rushes past the sides. Some of it flows up and over the roof, and it keeps going the way the wind blows.

As the air zooms past the corners, it skips the spot right behind the wall. That spot stays tucked away. Only a little wind reaches it.

We call a spot like that a shelter, which means a place that keeps the wind away from you. When you stand in the shelter, the wall takes the push instead of you.

Up on the roof, a flag flaps hard in the wind. Down in the shelter behind the wall, the leaves on the ground lie still. The same wind blows past both places.

The wall stops the wind, so the air slips around and leaves a shelter behind.

Behind the big wall, your coat hangs soft and your hair stays put. Past the corner, the wind keeps rushing by.