Small but dangerous wildfires broke out in bone-dry brushlands around Southern California on Friday as temperatures soared to triple-digit levels in some areas.

Firefighters chased outbreaks of fire in five counties as the region withered under the influence of a high- pressure system expected to last into the weekend.

A 45-acre fire broke out shortly before 11 a.m. in rolling hill country near Pomona in eastern Los Angeles County and burned within feet of some houses, said county fire Inspector Sam Padilla.

But ground crews aided by water-dropping helicopters made good progress and only smoldering hot spots remained by midafternoon.

"We pretty much got a great handle on it," Padilla said.

A 35-acre blaze in Ventura County's Piru Canyon was 60 percent contained by 100 firefighters, said Fire Department spokesman Bill Nash.

Nash said firefighting resources were prepositioned in anticipation of the heat and high fire danger and made quick work of the blaze. He said the fire was expected to be fully contained by 10 p.m. Friday.

In Riverside County, a fire in Corona was expected to be contained at five acres, said Massiel Ladron De Guevara, spokesperson for the California Department of Forestry and Fire Protection.

San Diego County firefighters contained a small brush fire that was ignited by downed powerlines near Ramona and were fighting brushfires of a few acres each near Valley Center and Poway. No homes were threatened and no injuries were reported.

Firefighters in San Bernardino County battled flames spreading through dry grass in the Chino Hills area but no homes were threatened.

Up in the eastern end of the San Gabriel Mountains, crews continued to work on a 461-acre wildfire that erupted Tuesday on the flanks of Mount Baldy. It was 72 percent contained and no injuries or building damage were reported.