(Reuters) - Power supply to about 150,000 California homes and businesses is expected to be shut off on Wednesday, in the latest precautionary outage planned by utility giant PG&E against wildfire risks posed by extremely dry, windy weather.

FILE PHOTO: PG&E works on power lines to repair damage caused by the Camp Fire in Paradise, California, U.S. November 21, 2018. To match Special Report USA-FUNDS/INDEX REUTERS/Elijah Nouvelage/File Photo

Late on Tuesday, the company said it would go forward with the shutoffs from 9 a.m., with some customers likely to be unaffected until late afternoon.

The mass blackout will be the fourth imposed by Pacific Gas & Electric Co, a unit of PG&E Corp, since Oct. 9, when about 730,000 customers were left in the dark as a preventive measure called a “public safety power shutoff.”

A precautionary outage initiated on Oct. 23 hit an estimated 179,000 customers, while another run in phases from Oct. 26 through Nov. 1 affected a record 941,000 homes and workplaces, according to PG&E.

The latest mass shutoff is likely to run through midday Thursday and could ultimately affect 181,000 customers across portions of 16 counties in northern and central California, PG&E spokeswoman Katie Allen told Reuters.

The outages are a response to forecasts for humidity levels to drop and heavy desert winds to howl through the region, a scenario that strengthens the risk of wildfires ignited by downed power lines.

Wind gusts will reach between 35 mph and 55 miles (56 km to 89 km), with isolated areas of higher gusts, National Weather Service forecasters said.

PG&E, California’s largest investor-owned utility, filed for bankruptcy in January, citing $30 billion in civil liability from major fires sparked by its equipment in 2017 and 2018.

That tally includes the state’s deadliest fire on record, the Camp fire that killed 85 people in and around the northern town of Paradise last year.

The recent wave of precautionary shutoffs has provoked criticism from Governor Gavin Newsom, state regulators and consumer activists as being too broad.

Newsom blames PG&E for doing too little to properly maintain and secure its power lines against wind damage and has accused the utility of poorly managing some of the mass outages.

Utility executives have acknowledged room for improvement while defending the sprawling cutoffs as a matter of public safety.

The California Public Utilities Commission recently opened a formal investigation of whether PG&E and other utilities violated energy regulations by cutting power to millions of residents for days at a time during periods of high winds.

Even as northern California braced for heightened wildfire risks, parts of Southern California, including Los Angeles, were expected to be doused by their first substantial showers after months of little or no rainfall.