The red-flag warning was originally issued for Los Angeles County from midnight to 6 p.m. Wednesday, but it was extended to 9 p.m. due to arid conditions and relative humidity as low as 5 percent.
A high-wind warning was issued until 3 p.m. for the Ventura County coastal valleys and local mountains.
Metrolink riders in Orange and Ventura counties experienced delays because of dangerous power lines and downed trees. Metrolink shut down service between Anaheim and Fullerton due to a power pole leaning on its side over the tracks.
A tree fell onto a truck around 10:30 p.m. Tuesday in Simi Valley. No injuries were reported. Authorities there said they received about a dozen tree-related calls overnight.
A high-wind warning was also in effect for the Inland Empire. Strong gusts blew sand and debris onto the San Bernardino Freeway. Drivers of high-profile vehicles were warned about gusty winds.
The wind knocked out power to Edison customers in Rialto, Rancho Cucamonga, Laguna Beach, Malibu, Simi Valley and Santa Ana. The company said crews were working to restore power.
A red-flag warning means the conditions can make a wildfire even more explosive. Fire crews have increased their staffing levels.
"L.A. County Fire Department and firefighters in the Southern California area will be ready for this wind event," said Capt. Mark Savage of the Los Angeles County Fire Department. "We need residents to also be prepared. Be aware we're in high fire danger. Anything they do that might contribute to the start of a fire could have devastating results."
Savage advised people not to throw cigarettes out the window and not use power tools in dry brush.
Officials advised anyone who sees smoke to report it immediately and not assume someone else has already called 911.