California's electrical grid operator issued rolling blackouts Friday evening – the first since 2001 – to combat the intense heat wave that has invaded most of the Western United States.
The California Independent System Operator around 6:30 p.m. local time determined that the state's power reserve had dipped below a critical threshold due to residents cranking up fans and air conditioning units in an attempt to stay cool as temperatures soared into triple digits.
The California ISO declared a Stage 3 emergency to help reduce the stress on the state's larger grid.
The rolling blackout – a procedure in which electricity delivery is stopped for non-overlapping periods of time – plunged as many as two million Californians into darkness over the span of four hours.
The emergency order was rescinded around midnight and power was fully restored to all households.
Anne Gonzales, a spokeswoman for California ISO, said grid operators will continue to monitor the ongoing heat wave throughout the weekend and into next week, as high temperatures are expected to persist until at least Thursday.