LOS ANGELES (BLOOMBERG) - California is asking residents and businesses to conserve energy on Wednesday (Aug 17) amid blistering heat to avoid overtaxing an already stressed electric system.

The state's main grid operator forecasts power demand will soar in the afternoon on Wednesday as residents crank their air conditioning, resulting in unusually tight power supplies. The conservation call is scheduled for 4pm to 9pm local time Wednesday, according to a California Independent System Operator statement on Tuesday.

Reducing energy can help stabilise the grid and prevent blackouts. Much of California's Central Valley is under heat advisories with a high of 102 degrees Fahrenheit (39 degree Celsius) forecast for Sacramento on Wednesday.

California energy officials have warned that the state is at risk of energy shortfalls during the hot and dry summer months. Among the reasons: diminished hydropower output during a devastating drought and the retirements of natural gas-fired power plants.