Fire officials are pushing back the estimated containment date for the Mountain Fire by four days.
Citing extreme terrain that is making fire-line construction difficult, crews now expect to fully surround the flames by Tuesday.
The fire has scorched more than 27,000 acres in the San Bernardino National Forest since it broke out south of Idyllwild on July 15.
It was started by electrical equipment near Mountain Center. As of Friday, containment is at 96 percent. Full containment had been previously expected by Friday.
Also of concern, with rain in the forecast, is the possibility of flooding and mudslides in the area, something that is not uncommon following a major wildfire.
"They do have a tendency to come together because we've taken away all the vegetation to help absorb water and help dilute and spread water out a little bit," said Idyllwild Fire Chief Patrick Reitz. "It can be a double whammy for folks living below the burn area."
Reitz added that the town of Idyllwild does not expect to see any flooding as a result of the fire, since it sits outside the potential fire drainage zone.