Why rainforests hug the equator and deserts sit in two dry stripes.
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Lands near the equator get lots of rain. Three big rainforests grow there: the Amazon, the Congo and the forests of Indonesia. The white blobs are clouds, not exact borders: the shapes are simplified.
Now look north and south. Big deserts sit in two stripes: the Sahara and Arabia up north, the Kalahari and Australia’s deserts down south. Red means hot, dry land, and again the shapes are simplified.
The sun beats down hardest on the equator. Hot air rises, like the shimmer over a hot road. High up it gets cold, and the water vapour in it turns to cloud and rain.
High up, the air flows away from the equator, then sinks near 30° north and south. Sinking air is dry, so deserts grow where it comes down. This loop is called a Hadley cell, and its bottom winds, blowing back to the equator, are the trade winds.
The rain belt follows the sun north and south through the year. Over Africa it gets furthest north, about 15° north of the equator, in August. Drag the Month slider and watch who gets the rain.
The dry stripes sit near 30° north and 30° south of the equator.
🌍 Play this lesson on the globe
The globe pictures are simplified to show the idea. Earth images: NASA Blue Marble (public domain).