Most of the Earth’s deserts are approximately 30 degrees both North and South. This fact is because these locations are characterized by descending dry air currents. Most deserts are hot and their latitudes run close to the equator. There is a name for the latitude that most desserts share, they are referred to as horse latitudes.
In horse latitudes the constant high pressure systems drive away the rain clouds. This is why the result is that it hardly ever rains in the desert. It can also help to explain why the temperatures are always so hot in most of the deserts.