A cool-down in weather has calmed a huge wildfire burning in Southern California coastal mountains as firefighters continue to cut kilometres of containment lines while conditions are favourable.

High winds and withering hot, dry air were replaced on Saturday by the normal flow of damp air off the Pacific, significantly reducing fire activity.

"The fire isn't really running and gunning," said Tom Kruschke, a Ventura County Fire Department spokesman.

Despite the favourable conditions, evacuation orders remained in place for residents in several areas.

Nearly 1,900 firefighters using engines, bulldozers and aircraft worked to corral the blaze.

The 111-square-kilometre blaze at the western end of the Santa Monica Mountains was 30 percent contained.

Firefighters said they had made "excellent" progress on Saturday in battling the blaze that threatened 4,000 homes near Los Angeles, nearly doubling the area under control, they said.

"With the milder weather conditions, firefighters are making excellent progress on extending fire containment lines," said an afternoon update from the Ventura County Fire Department (VCFD).

The inferno, the biggest of a series of wildfires fuelled by tinder-dry brush and soaring temperatures, could be fully under control by Monday, the department said.

The three-day blaze forced hundreds of residents to evacuate and damaged 15 homes in the rugged hills north of Malibu some 65km west of Los Angeles.

By Saturday the total area burnt remained at 28,000 acres - the same as Friday - "and that figure is not expected to change significantly," the VCFD said in an online statement.

Authorities re-opened scenic Pacific Coast Highway (PCH) - a section of which was closed on Thursday and Friday - although some local roads remained closed.

Source: Agencies