The Sonoran Desert covers nearly 100,000 square miles in southern Arizona, northern Mexico (state of Sonora), southeastern California, and northeastern Baja California. For many people, the word "desert" conjures up thoughts of sand dunes, intense heat, and strange reptilian creatures. But deserts can also be icy expanses such as the polar deserts of Antarctica or, in the case of the Sonoran Desert, they can be more temperate climates that support hearty cacti, lush plants, and abundant wildlife (including a few strange reptilian creatures - but, more on those later). What do all deserts have in common? Aridity. Deserts are dry places where rainfall is minimal - for example, Scottsdale's average annual rainfall is just over seven inches. Simply put, a desert will result anywhere significantly more moisture could theoretically be evaporated from the soil than is replaced by precipitation.