Less than two weeks after blacking out much of Northern California, the state's largest utility warned that dangerous fire weather could prompt another power shut-off to about a half-million people.

Pacific Gas & Electric notified customers that it could begin precautionary shut-offs to parts of 16 counties as soon as Wednesday, mostly in the Sierra foothills and north of the San Francisco Bay Area.

Blackouts would last at least 48 hours, the utility said.

The utility is concerned that winds forecast to hit 60 mph (97 kph) could throw branches and debris into power lines or topple them, sparking wildfires.

PG&E equipment has been blamed for igniting several of California's deadliest and most destructive fires in recent years. The utility, facing billions of dollars in potential claims, was forced into bankruptcy.

However, CEO Bill Johnson said shutdowns are about safety, not money.

"The sole intent is to prevent a catastrophic wildfire," he said.

A huge portion of California is under high fire risk amid unpredictable gusts and soaring temperatures.

In San Bernardino County, east of Los Angeles, three homes were heavily damaged, and six others received minor to moderate damage Monday evening from wind-whipped flames

A family of two adults and two children was treated for smoke inhalation and minor burns suffered during an evacuation. Two firefighters were treated and released from hospitals.

Earlier in the day Los Angeles firefighters beat back a blaze as it raced up canyon walls toward more than 300 multimillion-dollar ocean-view homes on a coastal ridge. None were seriously damaged or destroyed.

Firefighters were on the lookout for hotspots in anticipation of Santa Ana winds predicted to begin Wednesday night.

"This could be one of our most critical weeks of the fall season for fire weather due to very warm temperatures and bouts of Santa Ana winds," the National Weather Service said in a statement.

Southern California Edison, which had warned of possible outages at any time, announced Monday evening that none would take place in the next 48 hours but warned that it was monitoring the weather.

"Weather conditions might be different for Thursday," and in that case, notification would be given Tuesday, Edison spokeswoman Sally Jeun said.

PG&E's phone, text and email warnings to 200,000 homes and businesses came about 10 days after more than 2 million people had their lights turned off by the utility in response to powerful winds.

Johnson promised that if blackouts are necessary, the utility will work to do better at communicating with customers and avoid the chaos of the previous shut-off, when the utility only gave about 10 hours' warning to customers. Its website crashed, maps were inconsistent, and call centers were overloaded.

Panicked residents stood in long lines at supermarkets, hardware stores and gas stations, rushing to buy ice, coolers, flashlights, batteries and gas for their cars.

California Gov. Gavin Newsom and others blasted PG&E for the unprecedented size of the blackout and the communication problems.

Andy Vesey, a PG&E executive, has said the utility underestimated the needs of its customers and local governments.