Thousands of people were evacuated Friday and two major freeways were closed for a time.
"We got out what was important, and what's most important is us," said Christiane Elin, 30, who with her husband was among hundreds of people gathered at a high school serving as an evacuation center in Rancho Cucamonga.
About 12,600 acres have burned since the fire started Tuesday in the hilly residential areas near the San Bernardino National Forest.
For the week, about 20,000 acres have been scorched by several fires across Southern California.
Ash covered cars a half-mile from the fire in San Bernardino County, and billowing clouds of black smoke hung above the heavily developed area. The California Highway Patrol temporarily closed Interstate 210 and I-15, the main route to Las Vegas.
"It looks like nighttime here," said Kelly Bocanegra, an elementary school teacher.
Firefighters supported by water-dropping aircraft battled flames in back yards in Rancho Cucamonga, where four houses was destroyed Friday.
The fire also reached the outskirts of Fontana and Rialto in the sprawling suburbs about 50 miles east of downtown Los Angeles.
The flames were fanned by hot, dry desert winds of 25 mph and higher. The fire was only 17 percent contained.
Those unpredictable Santa Ana winds are the wildcard in the wildfire, reports CBS News Correspondent Vince Gonzales. And they're only expected to increase through the weekend. Officials are saying they may not see containment until sometime next week.
Forecasters said the wind would only get stronger.
About 30 miles west of the fire, a light dusting of ash fell on Santa Anita racetrack in Arcadia, the site of the $14 million Breeders' Cup World Thoroughbred Championships on Saturday.
Horses from North America and Europe worked out under a hazy sun as a huge plume of smoke hung in the distance.
"I hope it doesn't blow this way because the air quality would certainly be a concern," trainer D. Wayne Lukas said.
The fire, which authorities blamed on arson, was one of several that swept the region this week.
At Camp Pendleton Marine Corps Base, 50 miles north of San Diego, a 4,110-acre brush fire was as close as a mile from scattered ranches and homes.
A 2,857-acre arson fire in the Reche Canyon area of Riverside County that was contained Thursday destroyed five homes, a boat and several vehicles.