The wildfire that continued to rage Monday in Ventura County has been propelled by what experts describe as a remarkably dry year throughout Southern California.
The region hasn't seen a significant rainstorm since May, which has left brush around the Southland dry and brittle for much of the year.
Downtown Los Angeles has recorded less than half an inch of rain since July, compared with nearly 2 inches for the same period in 2005 and in 2004.
In the last few days alone, climatologists say they have been stunned by humidity readings.
A weather balloon above San Diego measured only 2% humidity, a reading normally reserved for places such as Death Valley. The region's average humidity for December afternoons is about 30% to 50%.
"These are some of the lowest humidities ever seen in the atmosphere," said Kelly Redmond, regional climatologist for the federal government's Desert Research Institute in Reno. "It's as dry as the air over the Antarctic."
The Southland's extended dry spell is caused by the same high-pressure system over the Great Basin that has dumped record rains in Oregon and Washington.
It is essentially the reverse of the 2004-05 season, which was the second-wettest on record in Los Angeles but left the Pacific Northwest in a drought.
This year's dryness has left Southern California and the West with more brush fires. In the last five years, there have been an average of 70,000 fires burning 6.6 million acres in the United States. So far this year, there have been more than 91,000 fires, burning 9.58 million acres, Redmond said.
On Monday, firefighters were dealing with three blazes -- the massive fire in Ventura County and two smaller ones in San Bernardino County.
The so-called Shekell fire near Moorpark ripped through the area Sunday, destroying five houses as well as a large, abandoned egg factory.
The blaze went uncontrolled for nearly a day as firefighters said they could not get water-dropping airplanes in the sky because of wind gusts that topped 70 mph.
Firefighters began to make headway Monday as Santa Ana winds calmed and aircraft were able to attack the blaze.
By Monday night, the fire had burned 13,600 acres and was 70% contained. About 500 residential structures were still threatened -- as well as citrus and avocado farms, cattle ranches, power grids, railways and highways -- but full containment was expected by 6 tonight.
Fighting the blaze were 1,529 firefighters, as well as air tankers, eight helicopters and 12 bulldozers.
The fire has consumed large expanses of parched chaparral, eucalyptus groves and grasslands that have seen increasing encroachment by suburban homes and ranches.
"We're in a meteorological pattern that is not giving us any relief," said William Patzert, a meteorologist with the Jet Propulsion Laboratory in La Canada Flintridge. "The meteorology has favored wildfires."
It also has brought about "alligator skin," sinus problems, chapped lips and even spiky, static-electricity hair, Patzert said, noting: "My eyes are itchy and I've been sneezing for days."
There's "a silver lining if you're selling ChapStick," he added.
Dr. Brian Johnston, emergency medical director for White Memorial Medical Center in Boyle Heights, said the dry conditions also bring headaches and nose bleeds, and sometimes worsen asthma problems.
But the biggest problem is wildfires. Fire officials said a good rainstorm in November usually reduces the fire threat -- but not this year.
Daniel Berlant, a spokesman for the California Department of Forestry and Fire Protection, said that unlike the rest of the state, Southern California has become a region under a nearly year-round fire threat.
"We have no plans to close [the] fire season in the south," Berlant said. "The conditions are year-round now."
Patzert said that the JPL weather station in La Canada Flintridge on Monday afternoon recorded remarkably low humidity rates: from 1% to 2%.
"Someone just told me they've never seen that," he said.
Patzert and other weather experts said the record rains that drenched Southern California two years ago caused an overgrowth of brush.
"That fueled us up," he said. "We were going to pay for that down the line."
The dry spell began in June, a month known for a cool coastal haze. But "June gloom" failed to materialize, and the month turned out to be the secondhottest since 1981.
By July, the entire state was hit with a record heat wave that resulted in more than 100 deaths, mostly among the elderly living alone.
Winter has seen little letup.
November was unseasonably warm, four degrees above normal. Now, December is shaping up to be warmer than usual by about three degrees.
Some rain could arrive by Friday, but the chance of that happening is only 20%, said Bill Hoffer of the National Weather Service in Oxnard.
Patzert said many meteorologists believe that mild El Nino conditions in the Pacific Ocean could yield a rainy winter, as early as January.
"That could be the white horse galloping over the horizon to save us," he said. "But right now it's a crapshoot."
Times staff writer Maeve Reston contributed to this report.