LOS ANGELES >> Wild weather and stifling heat had Californians seeking cool places, but steering clear of lightning-laced thunderstorms that were hitting the state’s beaches, mountains and deserts.

The sweltering but erratic weather was being generated by a high-pressure area coupled with a plume of moisture from Hurricane Linda heading off Mexico.

Thursday was expected to be the peak of the heat wave, with temperatures in the southwestern portion of the state reaching “dangerous levels” before gradually cooling starting on Friday, the National Weather Service said.

“All Southern Californians need to respect this heat,” the weather service wrote.

Downtown Los Angeles had a high of 101 degrees on Wednesday while the airport in suburban Long Beach hit 103, breaking the old record for the day of 98 set in 1990, according to the National Weather Service. In San Diego County, Chula Vista’s high of 99 was eight degrees above the 1990 record.

In San Francisco, temperatures soared into the 90s and reached triple digits inland Wednesday. But a breeze picked up and the area cooled off a bit by late afternoon.

Monsoonal thunderstorms lashed portions of Southern California in the afternoon, as they did a day earlier. More than an inch of rain fell in the Oak Glen watershed of the San Bernardino County mountains, the NWS said.

The deserts and foothills had brief but fierce downpours, and lightning strikes set several small fires in northern Los Angeles County.

Concerns about close lightning strikes prompted the closure of beaches in Long Beach. In Orange County, swimmers were ordered out of the water at Sunset Beach.

The downpour also caused a mudslide that forced the closure of Agua Dulce Canyon Road near the Antelope Valley Freeway.

Throughout California, hundreds of cooling centers opened in senior centers and libraries around California as people looked for ways to cool off.

Rikhardur Fridriksson, a tourist from Iceland, crouched under a row of trees near San Francisco’s City Hall with a big map of the city unfurled before him. He had planned to spend the day walking around outside. But after just 45 minutes in the heat, he was looking for ways to spend the day indoors, possibly at museums.

“I thought it would be autumn here,” he said. “I was definitely expecting cooler weather.”

The Los Angeles Department of Water and Power recorded the highest demand for electricity so far this year — 5,926 megawatts at 4:10 p.m. Tuesday, with an even higher reading expected Wednesday.

Sarah Wallin sat in the shade by a shallow fountain in a downtown park where her toddler rolled around and collected water in a bucket. She dipped her feet in the water.

“Our (air conditioning), frankly, can’t keep up with the heat,” she said.

Some schools dismissed students early amid the heat wave and air-quality alerts.

South of San Francisco, the Campbell Union High School District for the first time ended the day early and banned outdoor activities.

But National Weather Service Forecaster Diana Henderson said there is relief in sight. “It won’t be quite as bad toward the weekend. In (San Francisco) itself we are looking 86 degrees on Thursday, and then it plummets down to 80 degrees by Friday,” she said.