—Don Reichert, Duncanville, Texas It’s a combination of California’s climate and topography. First, the state receives more than 90 percent of its annual rainfall from November through April. Then the dry season begins. Hot weather soon arrives, and the land starts to bake. By late summer, strong and extremely dry winds make the terrain even more vulnerable. Still, while California is highly prone to fires, few are caused by a natural event such as a lightning strike. Up to 90 percent are sparked by human activity. Controlled burns (to rid the undergrowth of so much tinder) can help.