Temperatures soared above 100 degrees across the continent and forecasters in France and Britain predicted record highs on Wednesday.
In Spain, temperatures peaked at 106 degrees Tuesday in the southern cities of Seville and Cordoba, and reached 104 degrees in Madrid, the capital.
Three elderly women died in the southern Andalusian region and one died in Ciudad Real in central Castille, raising the overall death toll in Spain to 14 in a week of suffocating temperatures.
Doctors said the latest victims had heart or respiratory conditions that were worsened by the heat as Europeans suffer from one of the worst heat waves and dry spells in years.
In Paris, tourists sought relief in public fountains and in the shade near the Eiffel Tower.
"It's too hot to wait in line," said Karen Kauffmann, 54, a New Yorker visiting the French capital, where Tuesday's temperature of 100 degrees set a new record for August, according to the national weather service.
"We're drinking a lot of Coke — and water, stopping at cafes and hiding from the heat in the air-conditioned hotel," she said.
Temperatures also were high in Italy, even in the mountains. It was nearly 90 degrees in Cortina d'Ampezzo, one of Italy's most popular resorts in the Dolomites. Tour operators on the nearby Marmolada glacier kept skiers from the glacier runs that usually remain open during summer because of fears of landslides from melting ice.
At least 25 people have been treated for heat exhaustion, heat stroke and dehydration in the usually cool, northeastern city of Trieste, said Dr. Sergio Gregorutti of the Cattinara Hospital.
Workers in the Netherlands flooded a labor union with queries as to whether they could stay home because of the heat. They were told no, but they could wear shorts and take longer breaks.
Four nuclear power plants in Germany cut production drastically to avoid overheating water in cooling towers that empty into rivers.
Normally cool Britain also sweated as temperatures rose to 86 in London and Manchester, a northern city.
Bettors wagered on how much hotter it would get, the government warned about health dangers and trains ran slower for a second straight day out of fear the tracks might buckle.
It was so hot off Spain's Mediterranean coast that water temperatures were up by as many as three degrees from last summer, said Jorge Olcina of the Climatology Laboratory of the University of Alicante. In one stretch between Tarragona and Murcia, the sea temperature was 84 degrees on Monday.
The higher temperatures could cause the jellyfish population to flourish because heat accelerates their reproductive cycle, Olcina told the Spanish national news agency Efe. However, it would only be a passing phenomenon, he said.
The heat has exacerbated forest fires in Spain and neighboring Portugal, where two more bodies were found, raising the death toll from the worst wildfires in decades to 11.
Forest fires in the foothills of the French Riviera last week killed four people, and another man died on the French island of Corsica when he tried to put out a fire on his property. In Spain, firefighters have been battling intense fires since Thursday.
Back in Spain, an association of poultry producers warned of higher chicken prices because of lower supply: the heat causes chicks to take as many as 50 days to mature, compared with 45 normally.