The containment date for the Rim Fire was pushed to Oct. 27 this weekend as a pocket of unburned vegetation on its uncontained edge was deemed at risk for flare ups.
The previous containment date was set for Sunday after being delayed twice before.
The fire remains at 257,135 acres burned and 95 percent contained.
Michelle Carbonaro, spokeswoman for the Stanislaus National Forest, said the date was pushed back because fire authorities can't call the fire contained if the pocket flares up.
The area covers 500 to 1,000 acres near Kibbie Lake,a small lake to the northeast of Cherry Lake near 6,400 feet in elevation.
Even if the pocket ignites, however, the fire will burn itself out against the granite, she said.
She described the unburned pocket of vegetation as an island surrounded by granite and already-burned vegetation and said there would be little to no effect if it did catch fire besides delaying full containment and adding that acreage to the total lost.
"We're not going to put firefighters on the ground, because it's not worth the risk to their safety, with precipitation expected this week and the terrain still really difficult," Carbonaro said.
The fire must stop burning entirely before full containment can be declared. The date was pushed to the end of the month to allow expected precipitation to douse the remaining flames, Carbonaro said.
Crews will continue to patrol, mop-up and rehabilitate land as the fire's behavior is limited to creeping and smoldering, she said.
Personnel on the incident was reduced to 139 over the weekend.
A separate 2-acre vegetation fire started about 10 a.m. Sunday on Old Priest Grade Road. It was fully controlled about 4:30 p.m. and was caused by a truck, according to Cal Fire.