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Air evening things out

What Makes Wind Blow?

Uneven heating makes uneven pressure, and air always flows from high to low.

1 Sun heats theground unevenly2 Warm air rises,leaving lowpressure3 Air rushes into fill the gap
Wind is air correcting an imbalance.

  1. Step 1 of 5

    The Sun does not heat everywhere equally.

    Land Heats up quicklySea Heats up slowly

    Dark soil warms faster than water. The equator gets more direct sun than the poles. Every difference in temperature makes a difference in pressure.

  2. Step 2 of 5

    Warm air rises and thins out.

    1 Air is warmed2 It expands andrises3 Pressure at thesurface drops

    Heated air expands, becomes less dense and floats upward — leaving fewer molecules pressing down. That is a region of low pressure.

  3. Step 3 of 5

    Air flows from high pressure to low.

    High pressure Low pressureAir always flows this way

    Crowded air always pushes towards the emptier place. That flow is wind — and the bigger the pressure difference, the faster it moves.

  4. Step 4 of 5

    The steeper the difference, the stronger the wind.

    Storm gradientgaleModerate gradientfresh breezeWeak gradientbarely a stir

    A gentle pressure gradient gives a breeze. A steep one — the kind around a deep storm — gives a gale.

  5. Step 5 of 5

    Earth's spin bends the flow.

    Without Earth's spin Straight inWith it Curved — systems spiral

    Air does not travel straight from high to low. Earth turning underneath deflects it, which is why weather systems spiral instead of collapsing inward.

    Coastal sea breezes reverse at night: the land cools faster than the sea, so the flow turns around.

The short version

Uneven heating makes pressure differences, and wind is air flowing from high pressure to low.

Try it yourself

Open a door between a warm and cold room and hold a tissue at the top, then the bottom. It blows opposite ways.

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