Nearly 20,000 electric customers in the San Francisco Bay Area lost power because of high temperatures Sunday, a PG and E spokeswoman said. At 10:30 p.m. Sunday, 19,529 customers were in the dark with a majority of those in the East Bay and South Bay, spokeswoman Jacqueline Ratto said. Between 7:30 p.m. and 10:30 p.m. crews restored power to 22,500 customers. By 11 a.m. Monday, 2,944 customers still did not have power. The majority left without power are in the South Bay and the Easy Bay. "Severe heat in the Bay Area is causing widespread outages," Ratto said. PG and E has brought in extra crews and resources to restore power. Ratto said the widespread outages are generally due to increased demand for air conditioning. The increased demand may overload electric lines, transformers and other equipment resulting in power outages. And it's not over yet. Another round of high temperatures is expected to hit the Bay Area on Thursday.