Firefighters are battling a raging wildfire near Lake Tahoe in California that has destroyed more than 200 homes and forced about 1,000 people to leave.
The California blaze began on Sunday afternoon
California has declared a state of emergency and may seek federal help.
The number of firefighters deployed has risen to more than 700 but thick smoke has kept helicopters grounded.
In Alaska, fire crews were working to protect hundreds of homes in the Kenai Peninsula as a fire which broke out last week continued to smoulder.
The fire spread 81 square miles (210 sq km) before being slowed by rain.
High winds were hampering firefighters as they tried to tackle the fast-moving fire near the town of South Lake Tahoe in California's Sierra Nevada, fire officials said.
The blaze, believed to have been started by human activity, was reported on Sunday afternoon.
"It's like a 100-ft wall of flame that's marching through the forest," Leona Allen of South Lake Tahoe's fire and police departments' dispatch centre told the Los Angeles Times.
"It's thick with smoke. You can't see your hand. You can't see anything across the street."
Lt Kevin House, of the El Dorado County Sherriff's Department, said it was "far and above the biggest disaster that has happened in this community".
He said there were no reports of anyone missing but that officials had not yet been able to check the area affected.
Fire officials had been warning of a potentially active wildfire season in the Sierra Nevada after an unusually dry winter, the Associated Press reported.
The fire in Alaska broke out nearly a week ago and has destroyed dozens of homes and cabins in the scenic Kenai Peninsula.
An evacuation order has been in effect since Friday, although an unknown number of people refused to leave.
Fire officials said cooler, damper weather had helped crews fight the blaze. They hope to contain it before the arrival of drier weather forecast later in the week.
The area, some 80 miles (130km) south of Anchorage, is a popular hunting and snowmobiling destination.