Relentless heat was forecast for much of the eastern United States for a fourth consecutive day on Monday.
About two million customers are without power after thunderstorms and high winds killed at least 22 people, Reuters reports.
Power companies say could take several more days to restore electricity completely in some areas.
Emergencies have been declared in Maryland, Ohio, Virginia, West Virginia and Washington DC because of damage from the Midwest to the Atlantic Ocean.
Many schools and local governments are closed.
Temperatures in Atlanta reached a record 106 degrees Fahrenheit (41 degrees Celsius) on Saturday and 105 on Sunday.