LOS ANGELES (AFP) - Thousands of firefighters battled on Monday to contain wildfires in California that have forced the evacuation of thousands of homes and burnt more than 49,000ha of land.
They managed to bring number of fires down from 21 to 18, but a new fire erupted in Ventura county Sunday and was quickly dubbed the Chorro fire.
The biggest fire, the Rocky Fire, was sweeping through Colusa, Lake and Yolo counties north of Sacramento, the state capital.
More than 13,000 people have been forced to flee homes threatened by Rocky, CalFire spokesman Alisha Herring said.
Only 12 per cent under control, Rocky has burned through more than 24,200ha, destroying 50 structures, about half of them homes, and threatened 6,000 more, she said.
"It's the Rocky Fire that continues to really be a fast-moving fire that definitely continue toss challenge us today," CalFire spokesman Daniel Berlant said.
He said the fire ravaged through the forests at break-neck speed, with firefighters struggling to keep apace.
"Over the weekend, 20,000 acres (8,093ha) burned in just about a five-hour period. That's unprecedented historical rate of spread," he said.
The newly-sparked Churro Fire was burning across 500 acres (202ha) and was 15 per cent contained, Calfire reported on Monday.
A total of 49,000ha of land have burned so far, according to figures provided by the state.
California Governor Jerry Brown's office said that some 9,600 people were battling the fires early Sunday.
Weather in the drought-stricken state was the main culprit, with several thousand dry lightning strikes reported over the weekend.
"The drought is playing a huge role. With four years of dry conditions, our vegetation, the trees, the brush, are tinder dry," Mr Berlant said.
California is in the throes of a record-breaking drought, with much of the state completely parched.
The northern part of the state was the worst-hit, where forests were completely engulfed by the infernos, and several stretches of highway were forced closed.
In areas where fires had been put out, charred cars were all that was left behind on some roads, and trees were left smoldering on the blackened earth.
But Mr Berlant said firefighters were making headway on some fronts, with at least three fires extinguished since the weekend and other almost under control.
"We are making progress on several fronts. In fact several of the fires are near containment or almost completely contained," he said on CNN.
But, he warned there is no sign the dry, hot and windy conditions will improve, and said the coming months could see more fires.
"The dry conditions unfortunately will not get any better. We have several more months of fire season ahead until we get a bit of rain."
The National Weather Service issued a red flag warning for northern California, cautioning that "extreme fire conditions are occurring or imminent".
A state of emergency was issued on Friday, and the California National Guard has been called in, underlining the scale of the threat facing the western state.
A firefighter from South Dakota, Mr Dave Ruhl, 38, was killed on Thursday while fighting the Frog Fire in the Modoc National Forest outside Alturas.