Fifty six people have died during an 11-day heatwave which has scorched California and caused power blackouts leaving up to 1.5 million without electricity.

One hour before sunrise today the temperature had already hit 29C at the Central Valley city of Bakersfield, where later it peaked at 44C, the National Weather Service said.

Temperatures across the American state are today expected to be cooler by several degrees, but that still leaves many areas baking in 38C heat.

State and local authorities have reported at least 56 heat-related deaths, mostly among the elderly.

Up to 1.5 million residents across the state have lost electricity to their homes. In Los Angeles yesterday 26,000 people were left without electricity after hundreds of transformers exploded because of high demand and the heat.

"This is an historic heatwave," said Joe Desmond, Undersecretary for Energy Affairs, who added that it was the first time in 57 years that both northern and southern California had together experienced long heatwaves.

Thousands of dairy cows and other livestock have been killed by the heat. Farmers across California have been left with mounting carcasses of the dead animals and a backlog has been created at factories that turn the dead animals into pet food.

Several counties have declared a state of emergency, which allows the dead animals to be dumped in landfill sites, a practice that is normally illegal because of health risks.

Phil Larson, chairman of the Fresno County Board of Supervisors, said: "What can we do? We have to weigh the possible contamination to ground water versus a pile of dead cows stinking and attracting flies."

Milk production in California, a $5 billion industry, was down 15 per cent because of the temperatures, according to the California Farm Bureau.

Temperatures are expected to cool during the rest of the week.

Elsewhere across the United States, storms in St Louis have knocked-out power to 103,000 homes and businesses. And in the New York district of Queens a blackout has caused tens of thousands of people to be without power or air conditioning for nine days.

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