UPDATE 4-California fires rage on but some progress seen

(Recasts with Orange County fire threatening homes, details)

By Adam Tanner

SAN DIEGO, Oct 24 (Reuters) - Firefighters made headway against 18 wildfires blazing across Southern California on Wednesday as hot winds abated for the first time in four days, but they were still battling to save entire neighborhoods from hopscotching flames.

Around 9,000 firefighters worked the scorched hillsides and canyons while the skies were choked with thick, acrid smoke that forced residents to stay indoors or wear masks to protect their eyes and lungs.

San Diego County, at the southern end of the state, has been hardest hit, suffering losses in excess of $1 billion. Even as some of the 500,000 evacuees were allowed to return home, three major fires burned out of control there.

"It is just like a chess game as to which area is the highest priority. We are the highest priority now," said Jeff Terpstra, a fire chief at the Witch fire. "Some of this area hasn't burned for 25 to 45 years. It is destined to burn."

After the largest evacuation in California's modern history, officials combed areas for residents to return, looking for hot spots, utility breakdowns and looters before giving the all-clear.

"We should have almost all of our people back in their homes by this evening," San Diego Mayor Jerry Sanders said, referring to evacuees within city limits.

One of the most desperate fights was in Orange County, south of Los Angeles, where the 20,000-acre (8,094 hectare) Santiago fire that had defied the efforts of fire crews for days was threatening homes in a gated community.