Think heat, sun and thirst, and you've got a good idea of what the PCT's initial 648-mile (1,043-kilometer) section is generally like. The trail begins in a hot, dusty spot near Campo, a small town on the Mexican border at an elevation of 2,600 feet (793 meters). It winds through chaparral, scrub oaks and pines while temps soar to 90 and even 100 or more degrees Fahrenheit (32.2 to 37.7 degrees Celsius). There's little shade. Water sources are often 20 miles (32 kilometers) or more apart [source: Pacific Crest Trail].
The highest point in this section of the PCT comes in the San Jacinto Mountains, where the path rises to 9,030 feet (2,752 meters) and winds around granite peaks, subalpine forests and mountain meadows; it then plunges to its lowest spot (1,190 feet/363 meters) in San Gorgonio Pass. The trail continues across the San Andreas Fault Zone and western Mojave Desert, then enters the Sierra Nevada and the Central California section [source: Pacific Crest Trail].
The main challenge in Southern California is the extreme heat and lack of water. Even if you're only hiking a day, you need to make sure you're carrying plenty of water, plus know where you can obtain more. You should also know how to purify water, although on this stretch it can be difficult to find streams in some sections [source: Pacific Crest Trail].
Water isn't the only challenge here, though. The Southern California portion of the PCT is home to rattlesnakes, poison oak and flies, plus the innocuous-sounding Poodle Dog bush, a pretty, purple-flowered plant that can cause anything from a mild rash to severe respiratory distress if you touch it, or even if you touch clothing that has come into contact with the plant. It's best to wear long sleeves while traveling through the area [sources: Pacific Crest Trail, Pacific Crest Trail].