Hot, windy weather is expected to raise wildfire risk across much of California from Thursday through Saturday. Thousands of people could lose electricity as utilities take steps to keep their equipment from igniting fires.

In Southern California, Santa Ana winds are forecast to be strongest from Thursday afternoon to Friday afternoon. National Weather Service meteorologist Rose Schoenfeld said winds could reach 20 to 40 mph in the San Gabriel and Santa Susana mountains, with gusts of 50 to 70 mph. Parts of the Santa Lucia mountains also face a brief period of critical fire weather.

Los Angeles Mayor Karen Bass said she ordered fire crews and equipment into position before the winds arrive. She said the fire department also sought support from the state’s emergency services office.

Strong winds, heat and low humidity began affecting some Sierra Nevada communities Wednesday night, the weather service said. Its Red Flag Warning covers parts of central and Northern California from Thursday through Friday morning, when fires could spread quickly.