Heat wave sweeping across U.S. strains power grid: "People weren't ready for this heat"

Millions of Americans are under heat advisories as a relentless heat wave sweeps across the United States. Sweltering temperatures have settled over at least 14 states, straining the power grid in some parts of the country. 

California is urging residents to conserve air conditioning usage and set thermostats to 78 degrees Fahrenheit to prevent potential blackouts. In one example of the extreme heat, the state's Death Valley is seeing temperatures above 110 — at night. 

"When you've got really hot temperatures that don't cool down at night, that can be...