Hundreds of people have been evacuated in coastal Southern California and rural New Mexico as hot weather feeds wildfires, raising health concerns in other regions.
The blaze, which ignited on Wednesday in a wilderness area northwest of Santa Barbara, has consumed chaparral and tall grass in the Los Padres National Forest, and has now grown to 4,000 acres.
About 1,200 firefighters were trying to hold it as aeroplane tankers and helicopters dropped water, officials said.
"There isn't a lot of marine layer (ocean humidity) so not great conditions for firefighting," Diane Black, a joint incident command manager, said in a phone interview.
Winds drove the so-called Sherpa Fire toward the Pacific coast, leading authorities to evacuate two state beaches and some ranch land.
In New Mexico, the so-called Dog Head Fire that broke out on Wednesday about 10km northwest of the town of Tajique has forced evacuations and grown to more than 4900 hectares. Tajique is around 50km southeast of Albuquerque.
Governor Susana Martinez declared a state of emergency and activated the state's National Guard, ordering the unit to be prepared to assist if needed, according to a statement issued by her office.
The fire has burned through timber in central New Mexico, pushing heavy smoke towards cities more than 160km away as flames spread through a largely unpopulated area, fire information officer Peter D'Aquanni said in a phone interview.