Thousands of firefighters are battling nearly two dozen blazes across drought-parched California, while at least two of the infernos shut down kilometres of highway traffic, authorities and media said.
"Due to #RockyFire near Clear Lake, Highway 20 is closed from Highway 16 to Highway 53 for all through traffic in both directions," said CAL FIRE spokesman Daniel Berlant.
Berlant said on Twitter that the Rocky fire in Lake County grew to 22,500 acres and was five per cent contained.
Meanwhile firefighters took on another blaze in the Cajon Pass, shutting down several lanes of the 15 Freeway, The Los Angeles Times reported.
About 8,000 firefighters have been deployed across the state, said the California National Guard, which has been called into action. And a firefighter died while battling one of the blazes earlier in the day.
"California's severe drought and extreme weather have turned much of the state into a tinderbox," California Governor Edmund Brown said in a statement, declaring a state of emergency.
"Our courageous firefighters are on the front lines and we'll do everything we can to help them."
The dead firefighter was identified as Dave Ruhl, 38, from South Dakota, who was killed on Thursday while fighting the Frog Fire in the Modoc National Forest outside Alturas.
"Firefighter Ruhl will be remembered for his service and bravery and we extend our deepest condolences to his family, friends and colleagues with the US Forest Service," Brown said in a separate statement.
Wildfires are a fact of life in much of California, but were far worse than usual this year because of bone-dry conditions, with the western US state gripped by a fourth year of record drought.