The primary climate in the Southwest United States is Arid.

The Southwest United States is primarily characterized by an arid climate, which means it is generally dry with low annual precipitation. This climate is marked by hot summers and mild winters, with some areas experiencing extreme heat. The arid conditions contribute to the development of deserts like the Sonoran and Mojave Deserts. The lack of significant rainfall, combined with high evaporation rates, defines the region's landscape, with cacti and drought-resistant plants dominating the vegetation. Cities such as Phoenix and Albuquerque exemplify the arid climate, often experiencing scorching summers with temperatures exceeding 100°F.