Intense heat sears Southern California for 4th day

Intense heat seared much of Southern California for a fourth straight day Thursday as subtropical moisture triggered thunderstorms that caused torrents of water to push mud and softball-sized rocks across roadways and block one the state’s main north-south arteries.

As inland areas baked under triple-digit temperatures, firefighters from Menifee in Riverside County to Tehachapi in Kern County responded to multiple small brush fires, officials said.

But the worst of the weather struck along U.S. 395 in Inyo County.

A strong afternoon thunderstorm caused a 4-foot-high wall of mud to block both lanes of the highway near the Coso Junction area, about 130 miles north of Los Angeles, according to witnesses and the California Highway Patrol.

“It just rained and rained.... It just came down hard,” said Jerry Swab, who works at the Coso Junction Ranch Store, where stranded motorists waited for crews to clear the highway. The closure backed up traffic on the highway in both directions for several miles.

The powerful downpours also caused havoc on California 190 southwest of Owens Lake, where mud and softball-sized rocks were strewn across the roadway for about a mile, the CHP said. The agency said that motorists stopped to help clear some of the debris.

By Thursday afternoon, the temperature was 107 degrees in Woodland Hills and Chatsworth, 101 in Pomona and 105 in Lancaster, the National Weather Service said. Along the coast, it was 68 in both Malibu and Redondo Beach.

In Ventura County, it hit 108 degrees in Ojai while Camarillo peaked at 74. In Orange County, Lake Forest reached 99 degrees while Anaheim and Yorba Linda both hit 95, the weather service said. In the Inland Empire, it was 106 degrees in Chino, 109 in Lake Elsinore and 108 in Hemet.

The weather service said temperatures would begin to drop Friday, giving way to a dramatic cool-down over the weekend as low clouds and fog push inland from the coast.

The Los Angeles County Fire Department, which responded to about a dozen lightning-sparked blazes in mountain areas, said that the fire threat was still high and that crews would be beefed up Friday in places such as Malibu and the Antelope Valley.

“The fire weather is still here,” said Capt. David Chell.

In Riverside County, thunderstorms dropped hail in Hemet, Menifee and San Jacinto. Firefighters responded to three small brush fires in Borel and Menifee. One of the blazes, fanned by erratic winds, burned 11 acres before it was knocked down by 55 firefighters, who were aided by two helicopters and four air tankers, the Riverside County Fire Department said.

A blaze near Tehachapi scorched 55 acres and briefly threatened homes near Tucker and Highline roads before it was brought under control by about 30 firefighters, the Kern County Fire Department said.

robert.lopez@latimes.com