They don't need to. A gang of terrorists might read the Weather Channel website for predictions of Santa Ana winds. Just before one occurs, they can make hundreds of Dixie cup bombs--lighted cigarettes stuffed into matchbooks, each of which is then stuffed into a Dixie cup--then drive the roads through the hills and mountains of Southern California tossing them into the dry brush. The results could be catastrophic.
Most of these fires are started by arcing power lines from high winds. Jeez.