LOS ANGELES -- Critical fire weather is threatening California, as high winds, low humidity and dry conditions combine to form a sometimes lethal mix, the National Weather Service warned Monday.
A red flag warning is in effect for more than 3.8 million Northern Californians for the next three days, as wind gusts blow through the region.
In Southern California, Santa Ana winds will carry in warmer temperatures along with elevated fire dangers, forecasters said.
"We are looking at fall weather. Fall started early this morning," Scott McLean, a deputy chief with the California Department of Forestry and Fire Protection, said Monday. "So that means we're going to have significant winds that will be blowing in the north state as well as the south state with the Santa Anas."
The fire threat in the northern part of the state has prompted Pacific Gas & Electric Co. to consider preemptively shutting off power to about 21,000 customers in three counties, starting Monday evening. Such public safety power shutoffs are part of a strategy to reduce the risk of wildfires sparked by utility lines that break during extreme winds.
The shutoffs were expected to take place in portions of Butte, Nevada and Yuba counties in the Sierra foothills beginning about 5 p.m., PG&E said in a tweet.
The utility decided Monday afternoon not to proceed with evening shutoffs in Lake, Napa and Sonoma counties in the North Bay, and in El Dorado, Placer and Sutter counties in the Sierra foothills. PG&E said it might shut off power to parts of those counties Tuesday, depending on the weather.
"There's not a single factor that will drive a public safety power shutoff event, but we definitely look at the humidity, the temperature and the wind speeds," PG&E spokeswoman Megan McFarland said. She said the company began notifying customers in affected areas that shutoffs were possible. The notifications were made by robocalls, text messages and emails starting at 8 p.m. Saturday, she said.
In the town of Paradise, news of the preemptive measure provided little comfort.
PG&E announced -- then canceled -- a power shutoff just before November's Camp fire, which killed 85 people and became the deadliest wildfire in state history. Investigators with the California Department of Forestry and Fire Protection, or Cal Fire, later determined the blaze was sparked by a transmission line, which PG&E said would not have been included in any preemptive shutoff.