SACRAMENTO (AP/CBS13) — About 65,000 customers in 16 counties were impacted this weekend as part of a two-phase Public Safety Power Shutoff that will continue through Monday, Pacific Gas & Electric said on Saturday.

PG&E said it initially shut off power to 11,000 customers in starting at around 4 a.m. on Sunday. Power will be shut off Sunday evening to another 54,000 customers.

Impacted counties are Butte, Plumas, Shasta, Tehema, Alpine, Amador, Calaveras, El Dorado, Kern, Lake, Napa, Nevada, Placer, Sierra, Sonoma and Yuba counties, in addition to the Mooretown Rancheria tribal community.

The utility said that all customers should see their power back on by Monday night. The number of affected customers was originally said to be 89,000 until PG&E lowered that number on Sunday due to the scope of a forecasted wind event.

During the shutoffs, PG&E employees will check power lines for any damage. The company said it has opened up 28 community resource centers to help customers who lost power.

The shutoffs come as fire-weary California prepared for a new siege of hot, dry weather with potentially strong winds that could cause power lines to arc and spark new blazes in parched vegetation that’s ready to burn.

Red Flag warnings for extreme fire weather conditions were to go into effect in northern and central areas of the state at 9 p.m. Saturday and last into Monday, the National Weather Service said.

A second burst of winds was expected in those regions late Sunday into Monday, while in Southern California the most critical wind conditions were expected Monday although it was unclear how strong they would be.

More than 8,000 California wildfires so far this year have scorched 5,600 square miles, destroyed more than 7,000 buildings and killed 26 people. Several of the wildfire casualties occurred in Butte County, where the Bear Fire wreaked havoc and burned through the small town of Berry Creek.

Most of the loss has occurred since a massive outbreak of fires ignited by a freakish frenzy of dry lightning strikes in mid-August. The causes of other fires remain under investigation and authorities have said one was caused by a pyrotechnic device at a gender reveal event.

The renewed concern came with some 17,000 firefighters still on the lines of 25 major wildfires statewide, according to the California Department of Forestry and Fire Protection, known as Cal Fire.

Recent weather has been moderate, and Cal Fire said in a statement Saturday that firefighters have made “excellent progress.”

The new threat stemmed from predictions of a fall heat wave caused by a ridge of high pressure building off the West Coast that was expected to move eastward and settle on top of Northern California well into the coming week, the weather service said.

Such pressure causes dry, warming winds to flow from the interior toward the Pacific, reversing the normal flow of moist ocean air. Some canyons, passes and valleys are prone to high windspeeds as the air squeezes through on its rush offshore.

“A combination of the very dry fuels, low relative humidity values, and windy conditions will lead to dangerously critical fire weather conditions,” the weather service’s Sacramento office wrote.

The so-called Public Safety Power Shutoff programs used by PG&E and other utilities have been developed in response to disasters. Wildfires sparked by PG&E equipment include the wind-driven 2018 Camp Fire that destroyed much of the Sierra Nevada foothills town of Paradise and killed 85 people.

PG&E has said it is refining the process to narrow the scope and shorten the length of power cuts after being sharply criticized for intentional outages last year that affected millions of people and sometimes lasted for days. When high winds were predicted earlier this month, the utility was able to implement a shutdown that affected just 167,000 customers.

The utility also began airing 30-minute radio and TV programs during the weekend to familiarize customers with its wildfire safety process.

Numerous studies in recent years have linked bigger U.S. wildfires to global warming from the burning of coal, oil and gas, especially because climate change has made California much drier. A drier California means plants are more flammable.