What is a desert?
First, let's start with defining a desert. Areas receiving less than 10 inches of rain a year used to be considered deserts, but that included areas that didn't look like deserts. So now, to be considered a desert, the area receives less than 10 inches of rain and evaporates more than 10 inches of rain per year. There are four deserts in North America: The Great Basin, Mojave, Chihuahuan, and Sonoran.