LOS ANGELES, United States (AFP) — Crews battling wildfires ravaging southern California for a week have managed to slow the spread of the worst of the blazes, officials said Tuesday.

That fire called “Thomas” has charred nearly 95,000 hectares (234,000 acres) of land and is only 20 per cent contained, according to the state agency Calfire.

But in the past 24 hours that figure has risen by only a thousand hectares. Evacuation orders were issued for threatened areas in Montecito, Summerland and Santa Barbara.

Nearly 6,400 firefighters have been toiling for a week against blazes fueled by bone dry conditions and powerful winds. Santa Monica and Santa Clarita and part of the coast of Ventura County have been placed on red alert until Tuesday evening. For other areas the alert lasts until Wednesday evening.

Winds will blow at up to 65 km per hour (40 mph), forecasters said, as public health authorities urged people to wear face masks to protect against ash and smoke.

“Thomas” is the biggest fire ever recorded in Ventura County in terms of size and the fifth biggest in California’s history, said Eric Boldt, a meteorologist with the National Weather Service in Los Angeles.

It is the biggest of six blazes that have been burning since last Monday, but the others are now more than 90 per cent contained.

Altogether the fires have burned more than 100,000 hectares of land and forced the evacuation of hundreds of thousands of people.

Despite the intensity of the fires, which have left behind scenes reminiscent of a moonscape in many areas, authorities so far have reported one fatality — a 70-year-old woman who died in a car accident while fleeing from the flames in the Thomas area.

Damage from “Thomas’ alone is estimated at around US$48 million, according to the local TV station ABC7.

This has been California’s deadliest year ever for wildfires. More than 40 people died in October when fires swept through the state’s wine-producing counties north of San Francisco.

California governor Jerry Brown on Saturday said fires like these are the “new normal” and he linked them to global warming.