Deserts, arid climates, and dryland cover a good amount of the earth's surface. Environments with such a moisture deficit experience much less precipitation, which affects soil moisture as well as flora and fauna. There are many factors that play into the relatively low humidity of deserts and arid environments that experience little rainfall and absolutely no snowfall. These regions, however, are not necessarily always hot. And deserts are not always dry. And while arid climates may seem dull or barren to some, they are for others a complex arena where natural selection is more competitive than ever. It is their simplicity, in fact, that makes them good subjects for scholarly study.
Arid environments cover almost half the earth’s land surface and embrace a considerable range of environmental conditions. Terms such as arid, desert, and dryland are commonly used interchangeably and without strict scientific usage, though “arid” is also used as a formal division of drylands within the widely used classification scheme in UN Environment Programme 1997 (cited under Defining Arid Areas).
...[I]n North America, the Intermountain desert (which includes the Great Basin desert) is temperate, while the southwestern deserts (Mojave, Sonoran, and Chihuahuan) are extremely hot. Furthermore, winter rainfall is experienced in the Mojave Desert in southwestern California, both winter and summer rainfall occur in the Sonoran Desert, and predominantly summer rainfall is seen in the Chihuahuan Desert in Texas.