The extreme weather, caused by an influx of hot air from Africa, is also carrying loads of dust from the Sahara Desert across some parts of the continent.

Portugal has issued red health alerts for extreme heat for more than half the country, with thermometers approaching 46C on Saturday.

The country's highest ever recorded temperature was 47.3C in 2003.

In southern Portugal, the town of Évora was almost at a standstill on Saturday as only a few foreign tourists dared to venture out to take photographs of the Roman ruins called Diana's Temple.

Health officials issued reminders about the dangers that extreme heat can pose, especially for the elderly and the young.

The hot, dry conditions have led to several wildfires in Portugal.

Nearly 700 firefighters and 10 water-dumping aircraft are fighting the biggest outbreak, which has burned 1,000 hectares (2,470 acres) near the town of Monchique in the southern Algarve region.

"It's a very serious situation of extreme heat," Portuguese president Marcelo Rebelo de Sousa said.

The World Meteorological Organisation said continental Europe's heat record is 48C, set in Greece in 1977.

Forecasts indicate that the hot air from Africa, which turned parts of the sky a dark yellow hue because of the dust it carried, will not abate until early next week.

The torrid weather has been felt across Europe, as far north as Sweden.

Meanwhile, French energy company EDF has halted a fourth nuclear reactor - this time at the country's oldest nuclear plant at Fessenheim in eastern France.

Since Thursday, four French nuclear reactors in three power plants near the Rhine and the Rhone Rivers, including Fessenheim, have had to be temporarily shut down. EDF said the decision was made to avoid overheating the rivers.

Nuclear power plants use water from the rivers to cool down the temperatures of their reactors before sending the water back into the rivers.

Rivers that are unusually warm can experience mass fish die-offs, which has happened in Germany in the past week.