The wildfire, which started on August 14, has scorched 808sq km (312sq miles) in the Lake Tahoe area.
High winds are threatening to exacerbate the Caldor Fire in California, a blaze that has already forced evacuations near Lake Tahoe and in the neighbouring state of Nevada.
The National Weather Service warned on Wednesday that critical weather conditions through Wednesday could quicken the fire’s spread, as it already raced across treetops and drought-stricken vegetation.
The fire remained just outside of the city of South Lake Tahoe, as firefighters attempted to stop it from spreading to the usually bustling tourist area.
On Monday, 22,000 residents had been ordered to leave the area. A total of about 50,000 people have since been ordered to leave their homes in California and Nevada because of the Caldor Fire, with many monitoring the fire’s approach from hotels and makeshift shelters.
— Nick Vides (@vnick198) August 31, 2021
Stephen Vollmer, a fire behaviour analyst for the California Department of Forestry and Fire Protection, told The Associated Press news agency that the windy conditions had “created what’s called an active crown fire run, where the fire actually goes from treetop to treetop.”
He said embers were being cast up to 1.6km (one mile) out in front of the fire, creating new ignition points, including in some parts of the dense forest that have not burned since 1940 or before.
The Caldor Fire had already crossed two major highways and swept down slopes into the Tahoe Basin, where firefighters working in steep terrain were protecting remote cabins.
Cal Fire Division Chief Erich Schwab said some homes burned, but it was too early to know how many.
“The fire burned through there extremely fast, extremely hot. And we did the best that we could,” he told the AP on Tuesday night.
Hand crew cavalry marching along Santa Claus Dr toward fire on east side of Christmas Valley.
Fire is approcjing backside of homes right now.
— Scott Rodd (@SRodd_CPR) August 31, 2021
The Caldor Fire has scorched nearly 808sq km (312sq miles) since sparking on August 14.
As of late Tuesday, authorities said it was only 18 percent contained.
It is just one of dozens of fires that still burning in the state, as climate change during the last 30 years has continued to make the US West warmer and drier.
Scientists have said climate change will continue to make weather more extreme and wildfires more frequent and destructive.
“This thing is just unstoppable,” Lee England, who fled her South Lake Tahoe apartment late Sunday, told the Reuters news agency as she sat outside a recreation centre turned into a Red Cross shelter in Carson City on Tuesday.
No deaths have been reported in the Caldor Fire, but three firefighters and two civilians were injured in recent days.
Farther north in the Sierra, Crews were continuing to battle the Dixie fire on Wednesday.
It is the second-largest wildfire in state history at 3,317sq km (1,281sq miles).
The weeks-old fire was burning about 105km (65 miles) north of the Lake Tahoe-area blaze, prompting its own evacuation orders and warnings this week.