THE five-year drought that has disrupted the California economy and forced millions of people to turn off spigots is now taking a heavy toll as fires flare up around the state.The firestorm that swept through the exclusive residential hills of Oakland and Berkeley underlines the vulnerability of the essentially arid state to quick-moving blazes after five years of dry weather. Killing at least 12 people, destroying at least 400 homes, and causing hundreds of millions in damage, the fire was one of the worst in state history. A similar, wind-driven inferno last year destroyed 560 structures near Santa Barbara. Elsewhere, crews have been manning fire lines in a remote area of the Los Padres National Forest, just north of Ojai in southern California, and near Cloverdale. The blazes come after what has been a quiet summer in the Golden State. Unusually cool and gray weather has kept most fire fighters idle this year despite the drought. That all changed at 11 a.m. Sunday. Officials speculate that what was a small brush fire suddenly became an uncontrollable conflagration, fanned by 90-degree-plus temperatures and 30-mile-an-hour winds. Within hours, it had consumed more than 1,700 acres of prime real estate, leapfrogging million-dollar homes and shrouding the whole Bay area in ash-raining smoke. "I thought it was a simple grass fire," said one resident. "Then the sky just keep getting darker and darker." Surveying the damage by helicopter, Gov. Pete Wilson (R) quickly declared a state of emergency and said, "To call it devastation doesn't really describe it." Ironically, the calamity came almost two years to the day after a major earthquake rattled the Bay area. With remnants of that disaster still visible, such as hobbled transportation corridors, Oakland residents will now face years of rebuilding from the fire. The city has already been struggling to cope with an ailing economy, rising crime, and financially troubled schools. Several thousand people were evacuated from their homes to emergency shelters, hotels, and neighbors. Frantic to save their homes, residents placed sprinklers on roof tops, wielded fire hoses, and grabbed armloads of possessions. Hundreds of volunteers pitched in to help with shovels, rakes, and axes. Several dormitories were evacuated at the University of California at Berkeley. As many as 10 helicopters, 10 aircraft, and more than 1,000 fire fighters continued to battle the blaze at presstime.