The size of the fires surpasses a blaze last December in Southern California that burned 1,140.8 square kilometres.
"There's some challenges that firefighters are facing near the fire and in the area of the fire".
"There are also significant terrain hazards for firefighters". But Nguyen said these have not happened in the affected areas.
A firetruck rushes past flames that overran a road at the River Fire (Mendocino Complex) in Lakeport, California, U.S. July 31, 2018. The two fires, which have threatened more than 9,000 structures, have not merged, but officials are counting them as one.
NOAH BERGER via Getty Images Battalion Chief Matt Sully directs operations on the Ranch Fire, part of the Mendocino Complex Fire, burning near Clearlake Oaks on Sunday. It has burned through 225,000 acres - almost twice its size on Friday. The River and Ranch fires had grown to cover about 82,675 hectares by Saturday night, and were considered 32 percent contained, according to the California Department of Forestry and Fire Protection (Cal Fire).
Firefighters are unlikely to see some respite.
"There's nothing that California water policy has done that makes these fires worse or more hard to fight", Gleick said. "Everything is still dry".
Firefighters had to divert three very large air tanker passes as they worked to stop the fire from reaching the town of Lucerne because the "hostile" men wouldn't leave.
The Mendocino Complex Fire in Colusa and Lake counties near Ukiah, California, about two hours north of San Francisco, is now 283,800 acres and remains 30 percent contained, Cal Fire reported in its latest update at 7:33 p.m. local time Monday.
The White House did not immediately respond when asked about Gleick's comments.
"California's forests are burning because of past severe drought and current extreme temperatures and weather, worsened by human-caused #climatechange, which you think, in your fantasy world, doesn't exist", tweeted Peter Gleick, president emeritus of the Pacific Institute and a frequent critic of Trump's environmental policies.
The US president stated that California was diverting large amounts of water into the Pacific Ocean, while also failing to develop a sufficient number of firebreaks in dense vegetation. He's proposing to eviscerate government standards on fuel economy, which would mean more emissions of greenhouse gases, and proposing to revoke a waiver allowing California to set its own, tougher standards.
The water debate taps into a deep-seeded controversy in California: the balance between letting water flow through streams and redirecting it for agriculture and other uses.