LOS ANGELES (AFP) - At least nine wildfires remained active in California as of Sunday, the local authorities say, and hot and dry weather is hampering efforts to control the blazes.
Nearly 11,000 firefighters are in the field battling the fires, the California Department of Forestry and Fire Protection (CalFire) said in a statement.
At least five people have died in this year's wildfires, the authorities say. The blazes have forced thousands to flee their homes.
Most of the largest wildfires are between 47 per cent and 68 per cent contained, with three almost fully controlled, CalFire said.
However, a 485ha blaze dubbed the Tassajara fire that broke out last Saturday afternoon in Monterey County, along the state's central Pacific coast, is only 10 per cent contained, the department reported early on Sunday.
The weather also refuses to collaborate, with hot and dry conditions forecast throughout the weekend across the state.
Higher temperatures increase the chances of flare ups in fire areas that were already controlled, CalFire spokesman Daniel Berlant told Fox News.
Separately, Mr Berlant said that firefighters get especially frustrated when residents ignore danger warnings and refuse to evacuate.
Two people killed in the Butte wildfire in northern California chose to remain in their homes after they were told to leave because of the imminent danger, he said.
"Our firefighters this week were forced to stop fighting the fire and went into rescue mode just trying to get people to evacuate," Berlant told Fox.
The fires have cost California at least US$244 million (S$341.6 million) since July 1, compared with US$240 million for all of 2013. Last year, the bill amounted to US$434 million.
The deadliest fire in California's history was the October 1991 Tunnel fire that killed 25 people and razed 2,900 structures. In terms of land burned, the 2003 Cedar fire holds the record with more than 110,500ha destroyed.
Several other blazes are also burning across the country, including in the states of Washington, Oregon, Utah, Montana and Florida.