Wildfires that have been raging in California since the beginning of December are the worst in the US state’s history, officials said on Saturday. Some 259,000 acres (405 square miles) have burned so far and the flames have only been 40 percent contained. In terms of acreage consumed, the fire that started on December 4 now exceeds the devastating Rim Fire in 2013 by 2,000 acres. Steve Concialdi of the Orange County Fire Authority said the region has had "red flag" conditions for an unprecedented 13 consecutive days. Red flag conditions are when low relative humidity is combined with gusty, strong winds. Concialdi added: "As of this morning, were at 259,000 acres and still growing." The blaze northwest of Los Angeles grew by 3,000 acres overnight and although Santa Ana winds eased on Friday, they are expected to return with a vengeance over the weekend. And the fire is so large that winds on one end may be gustier than those on the other side. The 11-day-old Thomas fire surging through Ventura and Santa Barbara counties had devoured some 400 square miles of brush and timber and burned more than 1,000 buildings, including well over 750 homes. It also claimed the life of a firefighter Thursday. Another 18,000 buildings are still in jeopardy, including mansions in the wealthy enclave of Montecito, home to Oprah Winfrey and many other celebrities. No new evacuations have been called but the National Weather Service said winds in the area are gusting at around 30 mph. State fire officials said the blaze is spreading rapidly west.