A fire that has blackened nearly 2,900 acres in the San Gorgonio Wilderness east of Banning in Riverside County was 30 percent contained Wednesday.
More than 1,300 firefighters are battling the Hathaway Fire in century-old brush and dead trees.
"The fuel is really thick," said Carol Underhill with the San Bernardino National Forest. "We're talking about chapparral and timber impacted by drought and bark beetle kills. So, it's pretty tough circumstances that we're fighting in."
Nine air tankers, seven helicopters and 16 bulldozers were being used to fight the blaze and carve containment lines around it.
The fire broke out Sunday morning in Hathaway Canyon in the northern area of the Morongo Indian Reservation, about 85 miles east of Los Angeles.
Temperatures in the fire area are expected to be cooler - in the 80s - Wednesday. But the National Weather Service forecast also includes high winds for the area, with gusts between 30 and 35 mph or stronger on ridge tops.
The Incident Information System reported that motorists should be aware of increased fire-related traffic along I-10 and Oak Valley Parkway.
Correction: An earlier version of this story said that the map of the fire's perimeter had been updated on Tuesday rather than Monday.