Blistering heat blanketed much of the eastern United States for the third straight day on Sunday, after violent storms killed at least 13 people and knocked out power to more than 3 million customers.

Emergencies were declared in Maryland, Ohio, Virginia, West Virginia and Washington D.C., on Saturday because of damage from the storms that unleashed hurricane-force winds across and a 500-mile (800-km) stretch of the mid-Atlantic region.

The storms’ rampage came as sweltering temperatures topped 100 degrees Fahrenheit (38 Celsius) in several southern cities, including Atlanta, where the mercury hit an all-time record of 106 degrees F (41 C), according to Accuweather.com.

Over two dozen cities across 10 states set or tied all-time record high temperatures on Friday and Saturday, including Columbia, South Carolina; Knoxville, Tennessee; and Raleigh, North Carolina.

The heat wave continued Sunday for millions of people from the Plains to the mid-Atlantic.

Nashville broke another daily heat record Sunday, with a high of 104 degrees(40 C), according to meteorologist Brittney Whitehead of the National Weather Service. The old record for the day was 101, set in 1954.

“Highs will be in the low 100s for the rest of the week,” Whitehead said. The so-called Music City hit an all-time high temperature on Friday when it withered under 109 (42.7 C) degrees.

From St. Louis, Missouri, to Washington, temperatures flirted with more all-time records.

“It is very unsafe outdoors for those susceptible to these extreme conditions,” the National Weather Service said in a statement.

‘CATASTROPHIC DAMAGE” TO POWER GRIDS

Power crews worked to restore service to homes and businesses, and officials in some areas said the job could take up to a week, condemning many to days without air conditioning or even electric fans.

Utilities in Ohio, Virginia and Maryland described damage to their power grids as catastrophic.

Virginia Governor Bob McDonnell told a news conference at least seven weather-related deaths had been confirmed in the state.

“The scope and scale of the power outages, affecting virtually every region of the state, is almost unprecedented,” McDonnell said. As of early Sunday, more than 739,000 Virginia residents were still without power, authorities said.

Two Maryland residents died in the storm - one struck by a falling tree in Anne Arundel County, the other electrocuted after a tree crashed into a house in Montgomery County - said state emergency management agency spokesman Edward Hopkins.

Maryland Emergency Management Agency spokesman Ed McDonough said a Chesapeake Bay boater was still missing on Sunday and 639,000 customers remained without power.

In New Jersey, two cousins aged 2 and 7 were killed by a falling tree in a state park. And in eastern Tennessee, heat was blamed for the deaths of two brothers, aged 3 and 5, in Bradley County. They had been playing outside in 105-degree (41 C) heat.

HEATED LABOR DISPUTE

Ohio, where one storm-related death was reported, faced similar difficulties. Outages hit two thirds of the state with about one million homes and businesses left without electricity. Governor John Kasich said it could take a week to fully restore power.

President Barack Obama authorized the Federal Emergency Management Agency (FEMA) to coordinate all disaster relief efforts in the storm-ravaged state.

West Virginia was also hard-hit by storm-related outages, with about 614,000 customers without power, said Terrance Lively, spokesman for the state emergency management agency.

Further north, the storm caused outages from Indiana, where 135,000 customers lost power, to New Jersey, where Atlantic County declared a state of emergency and at least 206,000 customers were without power.

In northeastern Illinois, power utility Commonwealth Edison said outages affected about 210,000 of its customers, including 57,000 in the Chicago area, after a storm buffeted the region with high winds and hail.

In New York, a heated labor dispute threatened to compound problems posed by the summer heat wave, which has already put an added strain on the electrical grid for New York City and suburban Westchester county.

Power utility Consolidated Edison Inc locked out its unionized workers early on Sunday after contract talks broke down, both sides said, raising the possibility of power cuts.

The company said it had asked to extend negotiations for two more weeks but the union, which had threatened a strike by its 8,500 workers over a new contract, refused. In response, the firm told union members not to report for work on Sunday.

That left managers and any crews the company can hire to fix whatever problems arise as 8.2 million New Yorkers crank up their air conditioners to beat the heat.

Records for June were broken on Friday in Nashville, Tennessee; Louisville, Kentucky; Washington, D.C., and Atlanta. The temperature hit at least 104 F (40 C) in all four cities, according to the National Weather Service.

(Additional reporting by Brandon Shulleeta in Virginia, Susan Guyett in Indianapolis, Tim Ghianni in Nashville and Alistair Bull in Washington.; Editing by Tom Brown and Christopher Wilson)