‘Apocalyptic’ heat wave scorches US Southwest again

An extreme heat wave that has already shattered temperature records across the US Southwest threatened on Friday to push power systems to the brink of failure as residents cranked up air conditioners. 

California power grid operators, who have so far been able to keep the lights on, issued their latest "flex alert" for Friday, asking homeowners across the state to conserve energy in the late afternoon and evening when demand surges.