An estimated 1.5 million people in California are set to lose power on Tuesday as a utility firm tries to stop damaged cables triggering wildfires.
Pacific Gas & Electric (PG&E) said the shut-offs on Tuesday are a precaution as high winds are forecast.
It already faces an investigation by regulators after cutting power to almost a million properties in a bid to reduce the fires.
Wildfires fanned by the strong winds are raging in two parts of the state.
Thousands of residents near the wealthy Brentwood neighbourhood of Los Angeles have been told to evacuate because of a wildfire that began early on Monday.
Celebrities including the actor-turned-politician Arnold Schwarzenegger and basketball star LeBron James are among those who have fled the fast-moving Getty Fire, which started near the Getty Center arts complex.
Further north in Sonoma County, a larger fire has forced 180,000 people from their homes.
California's governor has declared a state-wide emergency.
On Monday regulators announced a formal inquiry into whether energy utilities broke rules by pre-emptively cutting power to an estimated 2.5 million people as wildfire risks soared.
They did not name any utilities but analysts said PG&E was responsible for the bulk of the "public safety power shut-offs".
The company filed for bankruptcy in January after facing hundreds of lawsuits from victims of wildfires in 2017 and 2018.
Of the 970,000 properties hit by the most recent cuts, under half had their services back by Monday, the Associated Press reported.
Despite criticism that the precautionary blackouts were too widespread and too disruptive, PG&E said more would come on Tuesday and Wednesday because further strong winds were expected.