Cover 30 % of the Earth’s surface and are situated mainly between tropical and subtropical regions north and south of the equator
The baking sun warms the ground in the desert during the day. At night, most of the heat radiates quickly into the atmosphere because desert soils have little vegetation and moisture to help store heat. This is why you roast during the day and shiver at night.
Air rising at the equator is warm and moist. As the warm, moist air rises, the air cools and the moisture condenses then falls as rain. The air currents spread out to the north and south, and descend around 30 degrees north or south of the equator. The descending air warms and dries the land, creating deserts.
Air pushed up over mountains cools and the moisture condenses and falls as precipitation. The sinking air on the other side of the mountain warms and dries the land creating deserts on the leeward side of mountains.