A classic Santa Ana is formed when high pressure over the Great Basin causes dry air to flow out of the interior of the West in a clockwise rotation and enter Southern California from the northeast and move toward lower pressure off the coast.
At least two structures have already burned and power outages have been reported across the county.
Citrus Street in Valencia was partially closed from Magic Mountain Parkway to Valencia Boulevard so that fire officials could move their incident command to the area.
"The prospects for containment are not good", Ventura County Fire Chief Mark Lorenzen said at a news conference Tuesday. Humidity will be in the 5-15% range.
The blazes brought evacuation orders for nearly 200,000 people, destroyed nearly 200 homes and have remained mostly out control.
Three firefighters were injured and taken to a hospital, where they were in stable condition, the Los Angeles Fire Department said on its website. At that speed, it would have covered Manhattan's Central Park in about 14 minutes. Firefighters were battling on the scene, being supported by water-dropping helicopters.
The fire grew five times its size in less than an hour, the Santa Clarita Valley Signal reported.
Some 7,000 homes from Santa Paula to Ventura were evacuated. "We lost everything, everything, all our clothes, anything that was important to us. Please pray for my city and everyone in it. I can't believe this".
Another Ventura resident, Samantha Wells-Zuniga escaped with her family and watched her entire apartment complex called the Hawaiia Village, burn down.
It was possible that some people had been trapped in their homes, he said, but sheriff's office personnel had gone to certain neighborhoods to ensure that residents were leaving.
They escaped with a few Christmas presents.
The fires have spread so quickly and grown so large thanks to the California weather phenomenon known as the Santa Ana winds.
According to officials, both fires were fueled by dry conditions and powerful winds. The oceanside city has a population of around 100,000.
