Germany's national meteorological service said July was on the way to being the hottest since records began in many parts of the country.

In France, an 85-year-old man admitted to hospital and an 81-year-old woman found dead in her home were the first people believed to have died there because of the heat. Officials said nine people were believed to have died.

"We must be vigilant and still more vigilant," said French Health Minister Xavier Bertrand. "And pay more attention to the vulnerable and those who live alone."

Britain launched an emergency plan of extra visits to the elderly and vulnerable. British bookmakers stopped taking bets temperatures would soar above 100 degrees Fahrenheit (37.77C) for only the second time -- the first was in August 2003.

The searing heat and expected storms later in the week threatened to damage northern Europe's wheat crop just days before the harvest, especially hitting Germany and France.

Electricity grids were straining. In Britain the national grid warned that blackouts could be possible because of increased demand from air conditioners.

France's main electricity provider EDF said it had to buy power abroad. Not only did demand rise, but the company had to curtail production to maintain safety at nuclear power plants cooled by river water.

The mayor of Paris announced free residential parking and advised people to avoid motorised transport to reduce the danger of ozone pollution.

EXTRA WATER

At Buckingham Palace, officials laid on extra water for 8,000 guests at a garden party for military veterans after several guests at a similar palace event fainted on Tuesday.

"There is shade for them, all the marquees are used, there's lots of helpers on hand for any guests who may feel unwell," a palace spokesman said.

The House of Commons issued a special "shirt-sleeve order" allowing journalists covering Britain's parliament to break with convention and enter the chamber without a jacket.

In the Netherlands, organisers cancelled a four-day walking event after two participants died of the heat on Tuesday. Firefighters handed out water to drivers stuck in traffic jams.

Police said a 14-year-old boy in central England drowned in a canal after he jumped in to cool off.

In Ireland, firefighters battled a gorse blaze close to a beach south of Dublin on Tuesday after temperatures pushed above 30 degrees Centigrade for the first time in more than a decade.