Power is set to be cut off for around 800,000 homes, business and other locations in Northern California, in an attempt to prevent wildfires.
Large swathes of the San Francisco Bay Area – though not the city of San Francisco itself – are expected to be affected.
The region’s utility company, Pacific Gas and Electric (PG&E), has warned the shut down could last several days, drawing anger from some residents.
With climate forecasts predicting excessive winds, the transfer is meant to forestall the danger of fallen energy traces from igniting the type of wildfires which have devastated giant areas of the state in earlier years.
Local shops reported an influx of customers buying up supplies for a black out that could, if the weather remains adverse, last for several days.
Many schools in the area have told students to stay at home on Wednesday and await further information for the remainder of the week.
Despite widespread frustration, local meteorologist Mike Pechner said the move was warranted.
“It’s not an overreaction at all. As the wind comes in, the wires, of course, oscillate back and forth. If they touch, they start a fire.
“None of us are happy about it,” said California governor, Gavin Newsom. “But this is part of something that we knew was likely to occur several months ago, when PG&E finally woke up to their responsibility to keep people safe.”
The warnings stretch north of the San Francisco Bay Area, in areas such as Napa and Sonoma, famed for wine-making. Further south, many cities synonymous with Silicon Valley giants could be affected, such as Cupertino, home to Apple.
The huge “Camp Fire” in the town of Paradise last year burned 150,000 acres and left 86 people dead. An investigation determined that poorly maintained PG&E equipment was to blame for starting the blaze – the deadliest in California’s history.