The Sonoran desert stretches from southwestern North America (Arizona and California) to the Baja Peninsula and State of Sonora in Mexico, covering nearly 127,000 square miles (Chaikin; Sonoran; Sonoran-Baja). Because the Baja California peninsula was once attached to western Mexico, the Sonoran Desert is found on both sides of the sea of Cortez and most of Baja California is part of the desert. The Sonoran desert is divided into four sub-regions, each with its own distinctive geography and flora. It consists of desert and xeric shrublands, and is relatively stable and intact.
The San Felipe Desert in the northeast part of the peninsula is the driest, with an average rainfall of 5 cm per year (Chaikin). The Gulf Coast Desert is a narrow strip that runs along the sea of Cortez from Bahia Los Angeles to the tip of the peninsula. This area receives moisture from tropical
storms and nearby mountains, which create arroyos and underground streams. On the Pacific side, the Vizcaino Desert is the largest sub-region, stretching from El Rosario 1000km to the south. Precipitation in this area is low, but plants receive moisture from the condensation of heavy coastal fog. South of the Vizcaino desert is the Magdalena Plains. Coastal mangroves, swamps, and large underground aquifers that support agriculture differentiate this region from the others.
Temperatures along the Baja California peninsula generally increase going south, and are higher at lower elevations (Chaikin). The Pacific coast is cooler than the Gulf coast. The desert is virtually absent of frost and summer temperatures often reach over 100F. Precipitation is low overall, but varies from place to place. There are two rainfall seasons on the peninsula: winter storms bring gentle rains from the pacific, but because of the mountain range, they usually do not rdach the gulf co'st. The wettest storms come in late summer or early fall, as chubascos, which are t...