The National Weather Service is warning of "critical fire weather conditions" through the weekend and placing a caution in effect across all of Los Angeles and Ventura counties through Sunday night.
The red-flag warning follows a trio of weather conditions that amplify fire danger: unseasonal temperatures, low humidity and high winds.
The weather service statement said the strongest winds are expected Saturday afternoon but could persist through Sunday.
City and county fire departments have deployed engines and personnel in fire-prone valleys as well as Malibu and Santa Clarita.
Authorities announced that Glendora Mountain and Glendora Ridge roads in the San Gabriel Mountains will be closed through Monday morning.
The precautions are necessary, in part, because California's prolonged drought has created tinder-dry vegetation, officials said.
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