Updated

Thunderstorms spit lightning and unleashed downpours across warm and humid Southern California on Friday, causing widespread power outages and injuring one man.

About 31,000 Southern California Edison customers lost power when storms hit Orange County about 9 a.m., and more outages were expected into the evening as storms continued elsewhere, the utility reported.

Fullerton College canceled classes and closed its 22,000-student campus due to an outage, the school's website said.

In San Bernardino County, a 50-year-old man was injured by a lightning strike on a crane at a construction site next to a hospital in Fontana.

It wasn't known if the man was touching the crane or was near it, but he was thrown hard to the ground by the lightning strike, said county Fire Department spokeswoman Tracey Martinez.

The victim was hospitalized with injuries that were not life-threatening, she said.

The area was hit by extensive dry lightning as erratic weather moved through, Martinez said.

"It's best to stay inside if you can," she said.

Southern California's thunderstorms were being fueled by subtropical moisture pulled into the region by a low-pressure area to the southwest, the National Weather Service said.

Thunderstorms were possible through Sunday, but some cooling should begin Saturday, forecasters said.

Thousands of San Diego Gas & Electric customers experienced power outages Thursday when similar wild weather swept through, City News Service reported. Lightning also started several small brush fires.

The thunder and lightning apparently scared many pets.

The San Diego County Department of Animal Services said its shelters took in 133 stray dogs and cats on Thursday, compared with 79 a week earlier.

"It was literally raining cats and dogs yesterday," department Director Dawn Danielson said in a statement urging owners of missing pets to look for them in shelters.

The unstable weather came on the heels of a heat wave that saw downtown Los Angeles reach 113 degrees Monday, the highest temperature ever posted there in 133 years of record-keeping.

On Thursday, 10 people were taken to hospitals for treatment of heat-related illnesses suffered during a cross-country event for high school students held at Pierce College in the Woodland Hills area of Los Angeles where the day's high was 97.

The Los Angeles Unified School District said 25 of its schools were among the 40 participating and it was reviewing the situation.

An LAUSD statement said coaches met beforehand and decided to proceed with the event, but a few students began to become distressed after a few races and the event was canceled at 4 p.m.