The PCT begins on a low hill near Campo (elev. 2,915′), a small town near the Mexican border. It then passes through Lake Morena County Park, tunnels beneath Interstate 8, and climbs through chaparral, scrub oak and pines to the rim of the Laguna Mountains. The trail dips into Anza-Borrego Desert State Park at Scissors Crossing, and then winds through the San Felipe Hills and lesser mountains of the Cleveland National Forest before crossing Highway 74 at 4,900 feet and climbing the backbone of the San Jacinto Mountains. It reaches its highest point in this section at 9,030 feet shortly before it plunges to its lowest point, crossing beneath Interstate 10 at broad San Gorgonio Pass (elev. 1,190′).
From here, the PCT climbs steeply to the crest of two east/west-oriented ranges, San Bernardino and San Gabriel ranges, often under welcome forest shade. It passes near Big Bear Lake and Lake Arrowhead before crossing Interstate 15 at Cajon Pass near Silverwood Lake State Recreation Area. The vistas from the trail in these mountains include the Los Angeles Basin and Mojave Desert. To the west of Mount Baden-Powell and the Angeles Crest National Scenic Byway, the trail descends to Highway 14 at Agua Dulce, and then traverses the often brushy landscape of the Sierra Pelona. It continues north for a typically hot and dry hike across the San Andreas Fault Zone and western arm of the Mojave Desert before climbing into the Tehachapi Mountains, where it crosses Highway 58 and enters the Sierra Nevada.
The southern California section ends where the trail crosses Highway 178 at Walker Pass (elev. 5,246′). The mountains of this section are bounded by faults that have been active in recent geologic time. Animals in this section include lizards, rodents, snakes, coyotes and cougars. Hummingbirds can be seen darting about, gathering nectar.
Flora encountered generally include desert scrub, chaparral or oak, with forests only at the higher elevations. Trailside water is often scarce in this section, particularly in summer, when temperatures range from the 80s to the low 100s.