Authorities say the Camp Fire in the north and the Woolsey Fire and Hill Fire in the south are being fanned by strong winds.
More than 250,000 people have been evacuated across the areas.
“The magnitude of the destruction of the fire is unbelievable and heartbreaking,” said Mark Ghilarducci, of the California governor’s office.
Where is the Woolsey Fire?
The blaze started on Thursday near Thousand Oaks, about 40 miles (64km) north-west of central Los Angeles. Another blaze, the Hill Fire, started at about the same time, also near Thousand Oaks.
On Friday, the flames jumped Highway 101 and headed into coastal areas. The fire now covers an area of about 35,000 acres (14,150 hectares).
The fire has also reportedly destroyed one of thesets for the TV series Westworld.
Where is the Camp Fire?
The 20,000-acre (8,100-hectare) fire north of Sacramento started in the Plumas National Forest on Thursday and quickly engulfed the town of Paradise. More than 6,700 homes and businesses were destroyed and residents fled for their lives. The flames moved so fast that some had to abandon their cars and escape the town on foot.
Butte County Sheriff Kory Honea told a news conference on Friday that the remains of five victims were found in or near burnt-out cars. Three others were found outside homes and one inside a home.
He said another 35 people were missing and three firefighters had been injured.
“This event was the worst-case scenario,” he said. “It was the event we have feared for a long time.”
Rescuers used a bulldozer to push abandoned cars out of the way in order to reach a hospital and evacuate patients as the fire engulfed the building, Butte County Supervisor Doug Teeter said.
“There’s nothing left standing,” said Scott Maclean, the state’s forestry and fire protection spokesman.