More than 350 firefighters, including some from Ventura County, battled a 350-acre wildfire in Los Padres National Forest on Wednesday that threatened homes near the San Marcos Pass and forced evacuations of residents.

By Wednesday evening, the flames were creeping closer to 30 homes nestled between the Santa Ynez Mountains and the coast, Nicole Koon, a spokeswoman with the county emergency operations center said.

The fire's southern flank was about 20 miles north of the Ventura-Santa Barbara County line late Wednesday afternoon, Larsen said.

"The fire could easily expand," said Larsen by phone from his Goleta office. "It all will depend on the weather."

Goleta is about 8 miles northwest of Santa Barbara.

About 150,000 Southern California Edison customers were without power shortly after 7 p.m. when thick smoke interrupted a transmission line near the fire, utility spokeswoman Lois Pitter Bruce said. Power was restored to about half of the affected customers about an hour later.

The fire was burning in thick, high brush that hasn't burned since 1950, said Kathy Good, a spokeswoman for Los Padres National Forest.

Water-dropping helicopters, including some from Ventura County, began flying early Wednesday morning, and firefighters are working to cut a containment line in the steep terrain where the fire is burning.

The Santa Barbara County fire comes as fuel moisture levels are "critically low," said Bill Nash, a spokesman for the Ventura County Fire Department.

"These low moisture levels make for extreme fire danger," Nash said, and come less than two days before the Fourth of July weekend.

Given the high fire danger, officials are "asking everyone to be extremely cautious" this holiday weekend, Nash said.

"If you see any suspicious behavior, don't ignore it," Nash said. "Report it."

Moisture levels across the county and much of the region are in a range not normally seen until the final weeks of summer, he said.

About 100 Ventura County Fire Department personnel were out of the county Wednesday fighting not only the blaze in Santa Barbara County but also fires in Northern California, Nash said.

The Northern California fires were started by a series of lightning strikes that hit dry brush or forest in June, igniting the vegetation.

While much of the state, including Ventura County, received some rain this past winter, it was not nearly enough to make up for the shortfall of rain in previous years, Nash said.

Despite the large number of firefighters that have been sent outside the county, Nash said the department still has enough personnel on hand to "protect Ventura County."

The department has about 560 members.

"We always pay attention to our mission to provide fire protection to Ventura County," he said.

Elsewhere across the state, there has not been enough firefighters. Gov. Arnold Schwarzenegger ordered National Guard units on Tuesday to help contain the wildfires in Northern California, which have been burning for a dozen days.

The fires have so far burned more than 660 square miles and covered much of the northern part of the state in smoke.

Meanwhile, fire officials in Santa Barbara County have issued evacuation warnings for areas above Glen Annie, Cathedral Oaks and Fairview canyons.

Santa Barbara County Fire Capt. Eli Iskow said 45 homes were evacuated and an additional 200-plus structures were threatened by the blaze.

— The Associated Press contributed to this report.