Sweltering temperatures across Southern California prompted calls Monday for electricity customers to reduce their energy use to help reduce strain on a system already weakened by the absence of the troubled Aliso Canyon natural gas storage plant.

Utility companies urged their residential customers to voluntarily delay washing clothes and dishes until bedtime and to keep their thermostats at 78 degrees or higher. In addition, the power companies asked business customers to voluntarily suspend unnecessary daytime operations such as production line work until nightfall.