Red flag warnings were posted at late morning and were expected to remain in effect through much of Friday due to predicted strong gusts and very low relative humidity, the National Weather Service said.
#RedFlagWarning in effect for Southern California from 10:00AM Wednesday morning through Friday at 6:00PM due to gusty winds and low humidity. This is #CriticalFireWeather so use caution outdoors. More tips: https://t.co/upBwccxXFO pic.twitter.com/ZOS1KBQzFH— CAL FIRE (@CAL_FIRE) November 23, 2021
The strongest and potentially damaging gusts were expected from Wednesday night through Thanksgiving morning. Gusts to 75 mph (121 kph) were expected near and below Cajon Pass and near the coastal foothills of the Santa Ana Mountains.
"Fire danger will rapidly escalate during the night," forecasters said.
The Santa Anas brought the prospect of public safety power shutoffs in high-risk areas to prevent wildfires from being sparked if the winds were to damage power equipment or blow debris into power lines.
EXPLAINER: Red Flag Warnings and their potential impact to California's wildfire season
Southern California Edison said power was cut to more than 8,000 customers in Los Angeles, Riverside and San Bernardino counties as of Wednesday night and shutoffs were possible for more than 170,000 customers in six counties.
San Diego Gas & Electric was considering shutting off electricity to more than 53,000 customers.
Forecasters also warned of a possible overnight hard freeze in the Antelope Valley north of Los Angeles.