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 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.