In Spain, helicopters dropped water on the flames as heat above 40 Celsius (104 Fahrenheit) and often mountainous terrain made the job harder for firefighters.
Shocked residents watching thick plumes of smoke rising above the central western Jerte valley said the heat was making their previously green and cool home more like Spain's semi-arid south.
"Climate change affects everyone," said resident Miguel Angel Tamayo.
A study published in June in the journal 'Environmental Research: Climate' concluded it was highly probable that climate change was making heatwaves worse.
At least 1,000 deaths have been attributed to the heatwave in Portugal and Spain so far. Temperatures in Spain have reached as high as 45.7C (114F) during the nearly week-long heatwave.
Spain's weather agency issued temperature warnings for Sunday, with highs of 42 Celsius (108 Fahrenheit) forecast in Aragon, Navarra and La Rioja, in the north. It said the heatwave would end on Monday, but warned temperatures would remain "abnormally high".
Fires were raging in several other regions including Castille and Leon in central Spain and Galicia in the north on Sunday afternoon. In Malagaprovince in southern Spain, wildfires raged into the night, affecting local residents near Mijas, a town popular with northern European tourists.
British pensioners William and Ellen McCurdy fled for safety with other evacuees in a local sport centre from their home on Saturday as the fire approached.
"It was very fast .... I didn’t take it too seriously. I thought they had it under control and I was quite surprised when it seemed to be moving in our direction," William, 68, told Reuters.
"We just grabbed a few essentials and just ran and by that stage everybody along the street was on the move," Ellen said.
In France, wildfires have now spread over 11,000 hectares (27,000 acres) in the southwestern region of Gironde, and more than 14,000 people have been evacuated, regional authorities said on Sunday afternoon.
More than 1,200 firefighters were trying to control the blazes, the authorities said in a statement.
France issued red alerts, the highest possible, for several regions, with residents urged "to be extremely vigilant".
In Italy, where smaller fires have blazed in recent days, forecasters expect temperatures above 40C in several regions in coming days.
Similar temperatures are forecast in Britain on Monday and Tuesday in what would top a previous official record of 38.7C (102F) set in Cambridge in 2019.
Britain's national weather forecaster has issued its first red "extreme heat" warning for parts of England. Rail passengers were advised to only travel if absolutely necessary and to expect widespread delays and cancellations.
DROUGHT IN PORTUGAL
Portugal's Health Ministry said late on Saturday that in the last seven days 659 people died due to the heatwave, most of them elderly. It said the weekly peak of 440 deaths was on Thursday, when temperatures exceeded 40C (104F) in several regions and 47C (117F) at a meteorological station in the district of Vizeu in the centre of the country.
By Saturday, there were 360 heat-related deaths in Spain, according to figures from the Carlos III Health Institute.
Portugal is grappling with extreme drought - with 96% of the mainland in severe or extreme drought at the end of June, before the recent heatwave, according to data from the national meteorological institute.
Emergency and Civil Protection Authority Commander Andre Fernandes urged people to take care not to ignite new fires in such bone-dry conditions.
In Greece the fire brigade said on Saturday 71 blazes had broken out within a 24-hour period. Local fire brigade officials on the island of Crete said on Sunday that a fire raging through forest and farm land had been partially contained.