"They haven't materialized yet, but we anticipate extremely strong winds by morning," said Dan Bastion of the U.S. Forest Service.
Firefighters spent the week building fire lines in an attempt to protect Ojai, Santa Paula and Fillmore from the Day Fire. But strong winds can cause "spotting," where embers are blown as much as a mile in front of the fire and can move the blaze past fire lines, officials said.
The last time the winds shifted, the fire on the Ventura-Los Angeles county line doubled in size in 24 hours. The fire that began on Labor Day in the Los Padres National Forest and has burned 112,257 acres, or 175 square miles. It was 39 percent contained.
Firefighters were able to take advantage of cool weather and overcast skies on Friday, covering hillsides with retardant and tearing through Chaparral with bulldozers while the blaze stayed mostly still.
Northeast winds were expected to begin hitting Southern California on Friday night. The National Weather Service issued a red flag warning of critical fire conditions through Sunday for mountains and valleys.