LOS ANGELES (AP) — Much of California simmered in a stew of high heat and humidity on Thursday, bringing thunderstorms, causing power outages and leaving some school kids in overheated classrooms.
The sweltering, erratic weather was being generated by a ridge of high pressure over the state and the monsoonal flow of moisture from Tropical Storm Linda, the weakening former hurricane spinning in the Pacific about 400 miles southwest of San Diego.
The weeklong heat wave, which has produced triple-digit temperatures up and down the state, was expected to start receding Friday.
Heat advisories extended from San Diego north to San Francisco and beyond, although fog that swaddled the Golden Gate and cooler temperatures along the immediate Bay Area coast presaged a gradual return to normal summer weather.
Cloud cover knocked a degree or two off high temperatures, but the National Weather Service said it would not be noticeable because of the high humidity.
Demand for electricity, meanwhile, was high as people turned to air conditioning for relief.
That proved a problem for the Los Angeles Unified School District, the nation's largest, where aging infrastructure was being taxed in a school year that now begins in mid-summer.
Maintenance workers had nearly 3,000 outstanding service calls for classrooms and offices, and when major repairs were needed they were taking a patchwork approach.
"We try to provide portable air conditioning units as much as possible," said Mark Cho, the district's head of maintenance. "But we don't have 2,900 portable units."
Cho said a dip in temperatures next week should give them time to make the needed repairs before the next heat wave hits.
Air conditioners across the region challenged the limits of the power grid. "Yesterday's usage was close to Southern California Edison's peak usage on Aug. 31, 2007," utility spokesman Paul Griffo said.
On Thursday afternoon, about 10,000 customers in Los Angeles and the surrounding region were without power, down from more than 15,000 a day earlier.
A cooling Northern California fared better with just a few hundred heat-related power outages among the 5 million customers served by Pacific Gas and Electric, utility spokesman Matt Nauman said.
Afternoon thunderstorms and resulting flash-flooding also left damage.
A section of State Route 2 in the San Gabriel Mountains northeast of Los Angeles was closed indefinitely because of a massive rock-and- mud slide triggered by a downpour. The California Department of Transportation estimated the debris between Islip Saddle and Vincent Gap amounted to 150 truckloads.
A 25-year-old man was killed earlier in the week when he was swept to his death by a rain-swollen creek in the Forest Falls area of the San Bernardino National Forest.
Forecasters, meanwhile, said the end of the oppressive weather was in sight but wouldn't happen overnight.
The high-pressure system bringing the heat will slowly weaken through Saturday while the tropical storm off Mexico also weakens, the weather service said. A trough of low pressure developing off the Northern California coast will be followed by an even deeper trough next week and there will be a gradual shift away from the hot and humid pattern, with thunderstorms restricted to the mountains and deserts.
The last day of the thunderstorm threat will be on Sunday, the National Weather Service office in San Diego said.