Every day firefighters in Los Angeles receive a brush burning index report that indicates the fire danger. If it's 165 or higher, that's extreme. The number for Thursday is 296, the highest it has ever been, according to Los Angeles Fire Chief Ralph Terrazas. Terrazas and other officials in Southern California warned residents Wednesday evening that a series of wildfires fueled by Santa Ana winds and dangerously dry vegetation likely was going to get even worse in the next 24 hours. "We stand a fairly good chance of a very challenging night and day (Thursday)," said Tim Chavez, a fire behavior analyst for CalFire, at a news conference on the 90,000-acre Thomas Fire in Ventura County. "There's a lot of potential for some large fire growth (for this fire)." More than 100,000 acres in Southern California have burned with little containment. Overworked firefighters caught a little bit of a break Wednesday when the winds eased somewhat, but the forecast for the next three days was bad news on top of bad news. The winds will pick up, with gusts up to 64 mph, before they taper down again. Humidity will be super dry -- less than 10%. Red flag warnings will be in effect through Saturday night, 24 hours later than originally predicted. Evacuations in some of the area's most affluent neighborhoods near the Skirball Fire affected 46,000 people, officials said.