Southern California is braced for "extremely critical fire conditions" caused by a new period of Santa Ana winds today through Wednesday across parts of Los Angeles and Ventura counties, as the battle to contain rampant blazes goes on.

"We are not out of the woods yet. Please stay on guard for a fast-moving fire," the weather service's Los Angeles office warned.

The threat of powerful wind gusts, combined with bone-dry humidity, in Los Angeles on Wednesday could test firefighters who have been battling to keep monstrous fires in Los Angeles in check since last week.