After several days of moderate weather and fog that helped firefighters battle the Gap fire near Goleta, officials are bracing for a heat wave expected to arrive today.

High temperatures in the mountains of Santa Barbara and Ventura counties are expected to reach 105 today and remain above 100 through Thursday, the National Weather Service reported. Triple-digit temperatures could last for several hours each day.

"It certainly will make the firefighting efforts more difficult," said Rolf Larsen, a spokesman for Los Padres National Forest.

The Gap fire has burned more than 9,600 acres in Los Padres National Forest near Goleta since it began July 1. Firefighters secured much of the southern and eastern flanks of the blaze Sunday, and containment stood at 35 percent on Monday.

Helped by cooler temperatures and humid weather, firefighters Monday worked to extinguish pockets of fire around Goleta and battled to keep the blaze from moving northwest. Firefighters also burned brush to strengthen containment lines.

Hoping to take advantage of the cooler weather before the heat wave, officials called in five "Hotshot" crews from Arizona and New Mexico, totaling 100 firefighters, to hike in or be lowered by helicopter into the Santa Ynez Mountains to thin brush and slow the fire's progress, said Stanton Florea, spokesman for the National Forest Service.

"The tactics are to jump on it when the weather's giving us the best advantage," said John Ahlman, another spokesman.

High temperatures make brush more combustible and contribute to fatigue among firefighters, said Capt. Drew Smith, a fire behavior analyst with the Los Angeles County Fire Department who was on his way to the Gap fire Monday.

Firefighters battling wildfires typically carry about 20 pounds of gear, including fire shelters, work boots, helmets, water and outer layers of fire-resistant Nomex, said Capt. Pete Jensen of the Ventura County Fire Department.

That's less than half what firefighters carry to structure fires, but still a lot considering the steep terrain of the site. Heat-related injuries are among the most common while fighting wildfires, Jensen said. On the up side, no significant wind is expected in the coming days.

Firefighters were worried about possible lightning strikes. Forecasters now say there is only a slight chance of thunderstorms, and they are unlikely to arrive before the weekend if at all, said Bonnie Bartling, a weather specialist for the National Weather Service in Oxnard.

So far, the Gap fire has destroyed four outbuildings and two firefighters have suffered minor injuries.

A total of 1,293 personnel are assigned to the blaze, which has cost an estimated $9.3 million in suppression efforts, officials said.

Early Monday, the fire threatened 2,811 homes and 228 commercial structures, but those assessments improved by the evening as fire information officials reported 251 homes, 176 outbuildings and no commercial buildings threatened.

More than 2,000 residents were able to return home Monday, said Roger Aceves, Goleta's mayor pro tem.

But some mandatory evacuation orders and warnings to be ready to leave remained in effect for scattered homes on the fire's growing western flank of the Santa Ynez Mountains, he said.

Investigators say the fire was caused by human activity but they have not determined if it was arson. Authorities are asking people with information on the fire's cause to call 961-5710.

Wildfires have burned more than 800 square miles and destroyed at least 69 homes throughout California, mainly in the north, over the past two weeks. One firefighter has died, from a heart attack.

Sunday's cooler weather also helped firefighters battling a 2-week-old blaze that has destroyed 22 homes in Big Sur, although fog hampered firefighting aircraft, said Sarah Gibson, a spokeswoman for the Big Sur fire command post.

The fire, which has charred 117 square miles, was 11 percent contained. Officials said crews were burning out brush between the fire's edge and Big Sur's famed restaurants and hotels to halt flames creeping down from ridges.

California's siege of fires began with a lightning storm in late June. About 1,450 fires have since been contained, but more than 330 were still burning Monday.

Gov. Arnold Schwarzenegger issued a health warning urging people affected by smoke to stay inside and limit physical activity.

— The Associated Press contributed to this report.