As Southern California scorched under punishing heat Tuesday, two fires broke out - one in Ventura County and another in Norco.
One blaze erupted northwest of Los Angeles in rural hills of Ventura County between the cities of Moorpark and Fillmore. It quickly grew to more than 200 acres and was expanding, fire Capt. Ron Oatman said.
Evacuations were ordered for scattered ranches and homes. Oatman couldn't provide a specific number but said numerous homes and electrical infrastructure were threatened. One small building was seen ablaze.
"Don't wait for an evacuation order if you feel like you're in danger," he said.
Air tankers and helitankers aided 150 firefighters on the ground. The weather was hot, with sustained winds of 15 mph to 20 mph and single-digit humidity percentages.
Another fire broke out in hills above homes in the Riverside County city of Norco, 40 miles east of Los Angeles. The city of about 26,000 is set in rolling terrain with hundreds of acres of parkland and horse trails.
Flames were whipped by the region's notorious Santa Ana winds, which blow from the northeast, speeding up and warming as they descend through mountain passes and canyons and push seaward.
The air is extremely dry, lowering humidity levels and making brush easier to burn.
Gusts of 30 mph to 40 mph were reported in Southern California's mountains, the National Weather Service said.
The Santa Anas also whipped up clouds of ash north and east of Los Angeles in the vast area of the San Gabriel Mountains burned over by a gigantic wildfire that continues to smolder a month after it began.
The winds caused some increased fire activity on ridgetops in the San Gabriels, but the haze was from blowing ash, not smoke columns, said Carol Underhills, a public information officer for the U.S. Forest Service.
The fire burned across 160,557 acres _ 251 square miles _ of Angeles National Forest after it was ignited by arson on Aug. 26.
At its peak it destroyed 89 homes and caused two firefighter deaths.
The blaze chewed through heavy growth in areas that hadn't burned in decades, leaving a carpet of ash in about a quarter of the 1,000-square-mile forest north and east of Los Angeles.
The fire remained 94 percent surrounded Tuesday, and fire commanders again pushed back the projected date for full containment, this time from Tuesday evening to Thursday morning, due to the weather.
Most of the remaining fire activity in the Angeles forest has been on the north side of Mount Wilson, the antenna-studded peak towering over suburban Pasadena and Sierra Madre, and in the Twin Peaks area on the east side of the fire, Underhills said.
The weather service also issued "red flag' warnings of fire weather conditions in other parts of California due to a combination of low humidity, high temperatures and wind.
Those areas included the hills east of San Francisco Bay and mountains to the north, the northern Sierra and northern Sacramento Valley and a large swath of the state farther north.
The red-flag warning went into effect at midnight in the mountains of Los Angeles County, which includes the San Gabriels and Angeles National Forest, site of the Station Fire. In the rest of the county, the warning was scheduled to take effect at 4 a.m.
Throughout the county, the red flag warning was scheduled to expire at 9 p.m. Thursday.
NWS forecasters said they expect winds of 15 to 30 miles per hour, gusting to 40 mph, in passes and canyons in the mountains of Los Angeles County, along with highs in the 90s at lower elevations and humidity of under 15 percent.
"The combination of very low humidities, offshore winds, hot temperatures and extremely dry fuels will produce critical fire weather conditions...," according to an NWS advisory.
In response to the heat wave, Gov. Arnold Schwarzenegger directed Cal/OSHA to carry out the "largest heat enforcement effort in its history" to protect workers, officials said.
Schwarzenegger also mobilized the California Emergency Management Agency and California Department of Forestry and Fire Protection to prepare for increased wildfire potential.
"California must be ready for any fires or heat-related illnesses that may occur as hot and dry conditions continue throughout the state,'' he said in a statement.
"I've directed our state's first responders to prepare for any situation that may arise and ensure that our resources are pre-positioned and ready to respond quickly,'' Schwarzenegger said.
The NWS forecast highs today of 81 in Newport Beach; 84 in Avalon; 85 at LAX; 89 on Mount Wilson; 96 in downtown L.A. and Long Beach; 97 in Anaheim; 99 in San Gabriel, Palmdale and Lancaster; 100 in Burbank and Newhall; 101 in Pasadena; and 104 in Woodland Hills.