The US Army is sending hundreds of troops to help tackle wildfires raging across parched California - and the state fire agency has warned about people flying drones in the affected areas.
A Pentagon spokesman said 200 troops from Washington state would receive three days' training before heading to California to help the 12,000 or so firefighters in the region.
"This is the first time since 2006 that [the military] has mobilised federal active duty military personnel [to fight wildfires]," he said.
Eighteen wildfires are raging in California, and 10 states around the country are reporting large fires, with the heat-wave exacerbating four years of drought and making California even more vulnerable.
State fire agency CAL FIRE cautioned of a growing problem of people flying hobby drones over affected areas.
"A collision with a hobby drone could easily result in major damage to fire-fighting aircraft, injuries to the pilot ... or worse, a mid-air collision," the agency said in a statement.
"If you fly, we can't!"
The Pentagon has already deployed four fire-fighting air tankers to help in efforts, with another 440 soldiers and airmen from the California National Guard mobilised as well.
Temperatures are expected to cool to more normal seasonal levels starting Wednesday in Southern California, but high winds will continue to threaten the spread of blazes.