Hundreds more people have been evacuated from their homes as wildfires continued to rip through France, Spain and Portugal, while European governments issued health warnings for the coming heatwave.

More than 1,000 firefighters have been battling since Tuesday to control two blazes in southwestern France that have been spread amid the blistering heat, extremely dry conditions and strong winds, leading to the evacuation of more than 11,000 people.

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In Portugal, temperatures have hit highs of 47 degrees Celsius this week, just below the national record. 

And while temperatures have now dropped a little, some areas are still expected to top 40 degrees Celsius, with five districts on red alert and more than 1,000 firefighters attempting to contain 17 wildfires, authorities said.

One of the planes that was battling forest fires in the country's north crashed on Friday, killing its pilot.

In Spain, a new wildfire broke out in the south of the country following other blazes in the west this week, with more than 400 people evacuated from the hills of Mijas, a popular Spanish tourist town in the province of Malaga. 

On Thursday and Friday, wildfires ripped through parts of Extremadura, which borders Portugal, and the central Castille and Leon region, forcing the evacuation of four more small villages. About 7,500 hectares of forest has so far been destroyed in the two regions.

Meanwhile, Italy's longest river and the lynchpin of its agricultural output, the Po, has been reduced to little more than a trickle in places, with temperatures expected to rise next week.

Health warnings

The extreme heat has prompted concern from European officials about the effects on people's health and on healthcare systems already challenged by the COVID-19 pandemic.

The World Meteorological Organization said the heatwave would reduce air quality, especially in towns and cities, warning that the stagnant atmosphere acted as "a lid to trap atmospheric pollutants. 

"These result in a degradation of air quality and adverse health effects, particularly for vulnerable people."

However, it's not just the medically vulnerable who are at risk. The UK Health Security Agency has raised its heat health warning to Level 4 – a "national emergency" which it defines as meaning "illness and death occurring among the fit and healthy – and not just in high-risk groups."

Portuguese Health Minister Marta Temido said the health system faced a "particularly worrying" week due to the heatwave and said some hospitals were overwhelmed.

From July 7 to July 13, Portugal registered 238 excess deaths due to the heatwave, while Spain reported 84 during the first three days of the extreme temperatures.

UK on track for record temperatures

Britain's weather forecaster issued its first ever red "extreme heat" warning for parts of England on Monday and Tuesday.

"Exceptional, perhaps record-breaking temperatures are likely early next week," Met Office Chief Meteorologist Paul Gundersen said. "Nights are also likely to be exceptionally warm, especially in urban areas," he said. "This is likely to lead to widespread impacts on people and infrastructure."

Ministers and officials are holding an emergency meeting on Saturday with temperatures expected to peak on Tuesday, with an 80 percent chance of the mercury topping the UK's record temperature. 

There is also a 50 percent chance of temperatures reaching 40 degrees Celsius somewhere in the UK. To date, the highest recorded temperature in Britain was 38.7 degrees Celsius, recorded in Cambridge on July 25, 2019.

"We hoped we wouldn't get to this situation, but for the first time ever we are forecasting greater than 40 degrees Celsius in the UK," said Met Office climate attribution scientist Nikos Christidis, who warned that climate change is not a warning for the future but a clear and present threat.

"Climate change has already influenced the likelihood of temperature extremes in the UK. The chances of seeing 40 degrees Celsius days in the UK could be as much as 10 times more likely in the current climate than under a natural climate unaffected by human influence."

Transport for London has advised its passengers to only travel for essential journeys, saying its staff would try to mitigate the effect of the extreme temperatures on the rails, overhead power lines and signaling equipment.

Hannah Cloke, climate expert at Britain's University of Reading, said the heatwave showed climate change had truly arrived and there was an urgent need to address the situation.

"We are seeing these problems now and they are going to get worse. We need to do something now," she said.

"It's harder to cope with these types of temperatures in the UK because we're just not used to them."