In scorching heat, the US is burning

Record temperatures have sparked devastating fires and storms

America's torrid summer is coming to a boil. While wildfires have consumed hundreds of homes in Colorado, and threaten hundreds more, temperatures in the 40s were causing misery in the eastern and southern United States. The heat has claimed the lives of at least three young children.

The pain was compounded yesterday with violent storms battering the eastern side of the country, killing 12 more people as trees were uprooted and three and a half people million people were left without power.

Marked in pink on a weather map of the United States, a heat warning has spread like a rash over a third of the country, from Nebraska east to New York and south to Florida. Such a warning is usually issued when the heat index – a combination of temperature and humidity – exceeds 38C and there is a risk of people and animals suffering heat exhaustion.

Many areas of the country have had no break from days of high temperatures and little rain, which have contributed to deadly and destructive fires in Colorado.

The worst fire in that state is in Waldo Canyon, Colorado Springs, but this is merely one among nearly 50 large, uncontained wildfires being fought across the United States.

Storm-related power disruption, meanwhile, has now affected several states, including Indiana, Ohio and New Jersey. In Virginia, Governor Bob McDonnell said the state had suffered its largest non-hurricane power loss in its history. Hailstones likened to coins were reported, scattered by a storm known by some Americans as a "derecho" – a name given to powerful thunderstorms spreading quickly in a straight line carrying gusts of wind at speeds close to 80 miles an hour.

The storm was thought to have swept across up to 600 miles in just 10 hours. There were concerns it could take up to a week for power to be restored in the worst-hit areas. Cars were crushed by falling debris and train lines have been blocked. A woman of 90 died in Virginia when a tree crashed through her home while she slept. Two cousins were killed when a tree fell on their tent as they camped in New Jersey.

President Barack Obama, below, promised federal assistance for Colorado's worst-ever wildfire as he toured the area damaged by the blaze, which has killed two people, destroyed hundreds of properties and forced 35,000 from their homes in and around the state's second-largest city. Mr Obama began his three-hour visit with a fly-over of the area left devastated by a fire that has raged for a week near the base of Pikes Peak mountain.

The Waldo Canyon fire unleashed its greatest fury last Tuesday night when it roared into foothill communities in the north-western corner of Colorado Springs and threatened a US Air Force Academy campus in town. By Friday afternoon, firefighters had managed to carve containment lines around 25 per cent of the fire's perimeter.

By Friday, the fire had scorched nearly 17,000 acres of timber and brush, much of it in the Pike National Forest west of Colorado Springs, about 50 miles south of Denver. Fire officials said 20,000 homes remained threatened, but evacuation orders were lifted for some of the estimated 35,000 residents chased from their dwellings earlier this week.

Authorities confirmed that 347 homes were destroyed in Tuesday's firestorm, most of them in the wealthy area of Colorado Springs known as Mountain Shadows. The tally of homes consumed by the Waldo Canyon blaze ranks as the highest on record for Colorado.

Aerial photos of the devastation unleashed by the fire showed large areas reduced to grey ash.

The Colorado Springs Police Chief Peter Carey said on Friday a second body had been found in the debris of a burnt-out home. The discovery of the first was announced late last Thursday.

The deaths bring to six the number of people who have perished so far this year in a Colorado wildfire season described by the Governor as the worst-ever in the state.

"This has been a devastating early fire season for Colorado. This community is heartbroken by the loss of homes," Mr Obama said to reporters as he walked along a street of burnt-out houses.

"We're lucky, because of the quick action that's been taken, that we haven't seen a lot of loss of life."

Mr Obama announced that federal money would be made available to local agencies and individuals affected by the blaze.

"We have been putting everything we have into trying to deal with what is one of the worst fires we've seen here in Colorado," Mr Obama said, speaking at a fire station where he shook hands with firefighters and praised them for their courage.

While authorities began allowing some evacuees to return last Thursday night, hundreds of residents from areas caught in the heart of a major firestorm remained homeless.

About 50 wildfires raged in other western states including Montana, Wyoming, Utah, Idaho, South Dakota, Arizona, New Mexico, Nevada and even Hawaii.

By Thursday, 21 aircraft tankers were being used for firefighting across these states, joining 170 helicopters, 550 fire engines and more than 8,800 firefighters around the country, said Jay Carney, a White House spokesman. The FBI is investigating whether any of the wildfires were started by criminal activity, but the cause remains unknown.

Elsewhere, more than 1,200 temperature records have now been broken across the US in the past seven days. Temperature records for the month of June were broken on Friday in Washington, DC, Atlanta, Georgia, and Louisville, Kentucky. In all three cities, the temperature hit 40C, according to the National Weather Service.

Friday's heat had spread east from the south-central plains and mid-Mississippi states, where temperatures continued to equal or break records on Friday.

The heat itself has proved deadly and is suspected to have caused the deaths of two young brothers, aged three and five, who had been playing outside in eastern Tennessee. Earlier in the week, a 39-year-old construction worker died at the University of Arkansas.

In Kansas City, Missouri, city health officials said they were investigating the deaths of three residents, including a baby boy, to determine if they were heat-related.

A strike by electrical workers could add to New Yorkers' misery. Union workers at the power company Con Edison could go on strike on Saturday, when a collective bargaining agreement expires, which could leave the company short-staffed to deal with power cuts as residents crank up the air-conditioning.

The weather is expected to stay hot through the weekend in the same areas of the country.

In Missouri, the Governor, Jay Nixon, ordered the activation of the State Emergency Operations Centre in response to fires and the prolonged period of heat and drought.

About 550 acres of the Mark Twain National Forest in the south-east of the state have already been burnt. Firefighters are struggling to protect a further 2,000 acres of the 1.5m-acre forest that are thought to be at risk.

In Tennessee, the temperature in Nashville on Friday reached 42.8C – breaking a record that dates back to 1952.

The state of Arkansas is in a drought, and many fireworks displays have been cancelled for the week of 4 July for fear of fire.