US storm-hit millions lack electricity amid heatwave
At least two million people remain without power in the eastern US following storms that have been blamed for 18 deaths since Friday.
Amid an ongoing heatwave, utilities warn it could take several more days to restore electricity to many households.
Maryland, West Virginia, Virginia, Ohio and the District of Columbia declared states of emergency over the weekend.
Power outages persisted on Monday from North Carolina to New Jersey, and as far west as Illinois.
'Hot and hotter'
With temperatures topping 100F (37C), many householders have no functioning air conditioning or refrigerators.
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Paul Adams
BBC News, Washington
It's not exactly crossing the Sahara on foot, but adjusting to life without power in Washington's leafy suburbs brings its challenges.
The first 24 hours after Friday night's storm triggered a host of questions: what on earth is a "derecho"? Why can't you leave lettuce in a fridge with dry ice? And how long will the basement stay cool, the longer this goes on?
While there's still hot water in the tank and fresh food in the house, it's an adventure. But after 48 hours, the adventure slowly sours. The dry ice is gone. The fridge, previously a treasure trove of fresh produce, is poised to become my enemy, armed with biological weapons.
Bit by bit, the basement is heating up. Nothing like the sauna upstairs, but not quite so welcoming any more. The big tree that came crashing down at the bottom of our road, bringing a tangle of power lines with it, sits untouched. It's going to be a while before the power comes back on.
And there's no sign of a break in the weather.
Officials are urging residents to check up on elderly or sick neighbours.
Bob Ambrosini, who had no power at his home in the US capital's suburb of Great Falls, told the Washington Post: "I've been living in the swimming pool."
More than 400 traffic lights were still not working in Maryland as of Monday morning.
But traffic congestion was lower than usual around the metropolitan Washington DC area as federal and state agencies allowed non-emergency workers to take leave or work from home.
Forecasters say there is no relief in sight: "Hot and hotter will continue to be the story from the plains to the Atlantic Coast for the next few days," the National Weather Service said.
Heat advisories are in effect for 17 states and all-time highs were expected again on Monday from St Louis, Missouri to Washington DC.
Further south, Atlanta reached an all-time high of 106F (41C) on Saturday.
The damage was mostly blamed on a meteorological phenomenon known as a derecho, where hurricane-force winds are buffeted ahead of fast-moving thunderstorms.
The storm swept a 500-m (800-km) swathe of the mid-Atlantic region on Friday night.
Another storm on Sunday brought wind gusts of up to 90 mph (145 km/h) and knocked out power to more than 200,000 people in north-eastern Illinois. Half of those remained without power on Monday.
Trees falling on homes and cars have been blamed for most of the extreme weather-related deaths.
Among the six people killed in Virginia was a 90-year-old woman who was asleep in bed when a tree fell on her home.
Two young cousins camping in New Jersey died when a tree collapsed on their tent. Two others died in Maryland, one in Ohio, one in Kentucky and another in Washington DC.
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Storm tracking online
Current power outages for Pepco, BGE, Dominion Virginia, and Potomac Edison
Cooling centres are open in Washington DC, Montgomery County, Prince George's County, Arlington County
BBC Weather explains the conditions behind the storm
The Federal Emergency Management Agency's storm response plus video explainer on how to beat the heat
The National Weather Service has a map showing high temperatures for the area on Monday
In other fatalities:
Coast Guard have abandoned the search for a man who vanished early on Saturday while boating during a storm off Maryland
A 77-year-old man died on Sunday night in Pitt County, North Carolina when a barn collapsed where he was parking a vehicle amid high winds
A tree killed a couple when it hit their golf cart in Beaufort County, North Carolina
Utility workers have been drafted in from as far away as Florida and Oklahoma to help turn the power back on.
Maryland Governor Martin O'Malley said he would ensure utility companies restored electricity quickly.
"No-one will have his boot further up Pepco's and BGE's backsides than I will," he said on Sunday afternoon, referring to the two main power firms serving the state.
The storm damage also caused online disruption, with Netflix, Instagram and Pinterest services temporarily disabled.