Officials ordered people in about 30 homes to evacuate Friday evening as a wildfire roared through a canyon in Southern California's Cleveland National Forest.

The homes were at the bottom of Silverado Canyon, where a fire that erupted earlier in the day had burned through 2 square miles of drought-dried brush in the midst of a heat wave. No residences were immediately threatened, and the evacuation was precautionary, fire officials said.

The fire had been burning uphill and away from the homes all day but there was a chance that a down-canyon wind could spring up after sunset, Orange County fire Capt. Mike Petro said.

"We don't anticipate any heavy winds. It would be light to moderate if they occur," he said.

About 300 firefighters, aided by aircraft, battled the flames, which sent up a towering column of smoke that could be seen for miles.

Crews worked in steep terrain and temperatures that still approached 90 degrees as dusk fell, with the high on Saturday expected to hit 102.

Crews dug firelines and helicopters dumped water on flames burning up the canyon walls.

"Because of the drought and the angle of the fuels, fire just races up canyon walls very, very fast. But when it reaches the ridgetop of these canyons, fire activity is going to decrease significantly, and that's when we're going to attack," county fire Capt. Larry Kurtz said earlier. "We're going to stop this fire at the ridgetop."

Cleveland National Forest sprawls over the rugged peaks of the Santa Ana Mountains straddling the Orange and Riverside county line southeast of Los Angeles.