Hot deserts are generally found in dry continental interiors in a belt at approximately 30°N and 30°S. It is at these latitudes where air that has risen at the Equator descends, forming a persistent belt of high pressure (anticyclone). This explains the lack of cloud and rain and high daytime temperatures. It also explains why, with the lack of cloud cover, temperatures can plummet below freezing at night during the winter. They are located there because by the time the moist air has travelled from the equator it has dried out.
Climate
A desert is an area that receives less than 250mm of rainfall per year. The resulting dryness or aridity is the main factor controlling life in the desert. Desert soils tend to be sandy or stony, with little organic matter due to the general lack of dense vegetation. Soils are dry but can soak up water rapidly after rainfall. Evaporation draws salts to the surface, often leaving a white residue on the ground. Desert soils are not particularly fertile.
Arid: Dry conditions typically associated with deserts. Hot Deserts: Regions of the world with less than 250mm of rainfall per year.