Cooler weather and light winds yesterday gave firefighters respite in their gruelling battle against a California wildfire that has forced 30,500 people to flee their homes.

A foggy layer of marine mist from the Pacific Ocean had drifted over the coastal town early yesterday after days of sizzling temperatures and powerful local gusts which sent the fire roaring out of control.

The fire, which has destroyed 80 homes, was 10 per cent contained and had burned through some 8,600 acres, according to the California Department of Forestry and Fire Protection (CALFIRE).

However fire officials expressed optimism yesterday that the break in the weather would allow them to make inroads into the blaze, which was now burning away from Santa Barbara and into mountain areas.

"The fire laid down last night and that was due to the weather," Santa Barbara County fire captain Dave Sadecki told NBC4 local television.

"Yesterday we had high temperatures, low humidity and extremely windy conditions; now we have decreased temperatures, increased humidity and we've got a layer of fog. That's all good for the firefight.

"Hopefully we can have a handle on it today and get those containment numbers up," he said.

An estimated 30,500 Santa Barbara residents are under mandatory evacuation orders, while on Friday officials said an additional 29,000 people had been told to prepare to evacuate.

Sadecki said although authorities wanted to get people back into their homes as quickly as possible, no unnecessary risks would be taken.

"We don't want people to return before it's safe," he said. "We want to restore Santa Barbara back to normal but we don't want to do it prematurely."

An army of around 3,455 firefighters has been deployed to tackle the fire, while on Friday three helicopters and a retardant-dropping DC-10 plane were bombarding the fire in a sustained aerial assault.