The 4,700-acre fire in Angeles National Forest is 46 percent contained.

LAKE HUGHES, Calif. (AP) – Despite withering summer heat, firefighters aided by planes slowly gained ground Wednesday against California wildfires that have burned more than 18,500 acres of brush and forest and caused hundreds of people to evacuate homes.

Wet weather headed into the region, bringing hope of relief but also raising fears of flash flooding and new lightning-caused fires.

The Federal Emergency Management Agency authorized funds for some of the blazes, which were burning in Los Angeles County, to the east in Riverside County, to the south in San Diego County and in Yosemite National Park in the Sierra Nevada.

One of the most difficult fires, 4,700 acres in Angeles National Forest on the edge of the Mojave Desert, was 46 percent contained.

The fire in Pine Canyon prompted voluntary and mandatory evacuations of more than 500 homes Tuesday, and an outbuilding and motor home were destroyed.

“The fire has been unpredictable, but now firefighters are trying to make a stand at Highway 138 – just north of the fire – to attempt to cut it off there,” said Los Angeles County fire Inspector John Mancha. More than 1,000 firefighters were on the line.

In Riverside County, a 3,698-acre blaze on the edge of San Bernardino National Forest was 50 percent contained as it burned toward unpopulated terrain. It previously posed a threat to the mountain communities of Idyllwild, Pine Cove and Garner Valley.

Nearly 1,200 firefighters worked the blaze. One firefighter suffered a broken leg.

Elsewhere in the county, a 350-acre fire southwest of Lake Elsinore was 90 percent contained and people who had evacuated from the Bundy Canyon area returned home.

In eastern San Diego County, an 8,500-acre blaze sparked by illegal fireworks was 66 percent contained and was expected to be fully surrounded by nightfall Wednesday. Some 1,300 firefighters battled the flames, which started as two fires Tuesday near Lake Henshaw.

Two outbuildings were destroyed and four firefighters were treated for minor injuries, said California Department of Forestry Firefighter Tyler Ashton.

The fire prompted evacuation of about 100 rural homes and about 200 youngsters from a Boy Scout camp Tuesday, but structures or communities were no longer threatened, Ashton said.

In the Sierra, hikers were evacuated and trails were closed in part of Yosemite National Park after a lightning-sparked wildfire grew to 1,300 acres Tuesday. The fire was one of nine fires burning in the park from lightning strikes two weeks ago, the National Park Service said.