Firefighters in southwestern France have battled to contain massive forest wildfires and Britain has recorded its highest-ever temperature, buckling train tracks and igniting grassfires in dry conditions around London.
Southern and western Germany and Belgium were also braced for potentially record-breaking temperatures on Tuesday as the heatwave, which scientists attribute to climate change, edged north and east.
A wildfire fuelled by strong winds raged on a mountainous area near homes on the outskirts of the Greek capital, prompting authorities to order the evacuation of four areas.
Numerous wildfires were reported in Italy. One of the biggest blazes broke out on Monday night in the hills of Massarosa in Tuscany, and was still raging on Tuesday afternoon.
"Fire continues to devour the woods in a frightening way due to the wind," the governor of Tuscany, Eugenio Giani, said. He said 365 hectares of land had been destroyed.
Fires were also reported in woods near Rome, as well as on the shores of Lake Orta north of Milan and near the northeastern city of Trieste, forcing the authorities to close a motorway and railway line, with temperatures set to stay high.
A temperature of more than 40C was provisionally recorded for the first time in Britain, the Met Office said.
Authorities have put Britain on a state of "national emergency" over the unprecedented temperatures. Train routes were cancelled and electricity companies reported mass outages. Network Rail tweeted pictures showing bends and kinks in the tracks.
To the east of the capital a large fire engulfed homes in the village of Wennington. Elsewhere large grass areas around the capital were on fire.
In southwestern France, the wine-growing Gironde region saw its biggest wildfires in more than 30 years and authorities said a man had been detained on suspicion of arson.
The fires have spread across 19,300 hectares in the countryside surrounding Bordeaux since July 12, forcing 34,000 people to leave their homes.
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About 2000 firefighters, supported by eight water-bomber aircraft, were battling the blazes.
With human-caused climate change triggering droughts, the number of extreme wildfires is expected to increase 30 per cent within the next 28 years, according to a February 2022 UN report.
"We are seeing more frequent heatwaves, and the heatwaves are hotter than they would have been without climate change," Friederike Otto, senior lecturer in climate science at Imperial College London, told Reuters.
The health impact of the heatwave has been in focus, with particular care given to the elderly and vulnerable.
Hot night-time temperatures were also hindering firefighting responses across Europe and worsening health conditions as the night hours failed to provide a cooling reprieve, experts said on Tuesday.
In Italy, temperatures were expected to hit 40C across a swathe of the north and centre throughout the week, as well as in the southern heel of Italy's boot, Puglia, and the islands of Sardinia and Sicily.
Five cities were placed on the highest red alert because of the heatwave on Tuesday. The alert will cover nine cities on Wednesday, rising to 14 on Thursday, including many of Italy's largest metropolitan areas, including Rome, Milan and Florence.
Although the mercury dipped back towards more normal summer levels in Spain and Portugal, firefighters in both countries were still battling multiple blazes.
More than 30 wildfires continued to ravage parts of Spain, with authorities paying special attention to four blazes in Castile and Leon and Galicia.
In neighbouring Portugal, around 50 municipalities, mainly in central and northern regions, still faced "maximum risk" of wildfires, according to the IPMA weather institute.
Australian Associated Press