Utilities urged customers to ease up on electricity use and officials opened cool shelters as California continued to swelter under a heat wave Friday.
Meanwhile, cloudbursts laced with lightning unleashed downpours in the mountains and deserts, leading to flash flood watches and warnings. Firefighters also watched for lightning-sparked wildfires.
The steamy conditions were expected to continue into midweek.
"When I opened the door, the heat almost knocked me down," Joan Porter told KCAL-TV as she sat in an air-conditioned senior citizens' center in Altadena, a foothill community northeast of Los Angeles that topped 100 degrees.
A Los Angeles utility reported power outages to nearly 4,800 customers with high demand. Meanwhile, a regional utility said it supplied a record amount of electricity to some 13 million people in Southern California and attributed the power demand to increased use of air conditioners.
The hot weather began Wednesday and may have played a role in the death of an 81-year-old hiker who became exhausted and ran out of water in inland Riverside County.
The heat also may have played a role in the crash of two small planes taking off hours apart Thursday at an airfield east of Sacramento, officials said. Two people died and two critically injured in one crash, and two were injured in the other crash.
The thinner warm air may have provided less lift for the planes as they took off, suggested Bob Petersen, air squadron commander for the El Dorado County Sheriff's Department.
Meanwhile, the state entered the peak two months of its fire season, when historically the most devastating blazes have occurred, said Daniel Berlant, a spokesman for the California Department of Forestry and Fire Protection.
Aircraft patrolled the Sierra and other wilderness areas to spot remote wildfires. Visitors swarming into the backcountry over the Labor Day weekend increased the risk of fires from improper or illegal campfires, Berlant said.
Officials also announced charges against two men and a cattle ranch suspected of recklessly starting a fire that has burned for nearly two months in central California.
The heat was expected to strain the state's electricity generating capacity, although no shortages were predicted. The California Independent System Operator, which oversees the state's power grid, urged customers to continue conserving electricity.
Southern California Edison said its energy load peaked at an all-time high of 23,303 megawatts Friday afternoon, surpassing the previous record of 22,889 megawatts set on July 25, 2006.
The Los Angeles Department of Water and Power said crews were working to restore power to 4,798 customers, said utility spokeswoman Kim Hughes.
Meanwhile, the Tennessee Valley Authority, the nation's largest public utility, said Friday that the recent heat wave in its seven-state region helped create record electricity demand.
The TVA set 13 peak power demand records — more than one every three days — during the month of August, TVA spokesman Gil Francis said Friday.
The federal utility set an all-time record of 33,499 megawatts on Aug. 16 when the average temperature in the valley hit 103.6 degrees — the highest average for TVA's region in 55 years.
A thousand megawatts powers about 550,000 homes in the utility's coverage area, which includes most of Tennessee and parts of Alabama, Mississippi, Georgia, Kentucky, North Carolina and Virginia.