About 220,000 people have been evacuated in France, while in neighbouring Spain more than 75,000 people have been told to leave their homes and a further 30,000 ordered to shelter in place, authorities said over the weekend.
The French blazes, which broke out last week near the Atlantic coast, are now only 15 kilometres from entry points to the main metropolitan area of Bordeaux.
"This is a fire of a size never seen before," Jerome Steffe, mayor of Cestas, said on Monday. Cestas is one of the suburbs just outside the main Bordeaux city area.
In Spain, fires were burning in the central provinces of Madrid, Avila and Toledo. Flames have devastated more than 50,000 hectares of countryside in Avila, making it the biggest wildfire in Spain's recent history, according to Environment Minister Sara Aagesen.
A separate blaze in Spain's eastern Castellon province has ravaged over 6,500 hectares, regional authorities said.
The wildfires around Bordeaux in southwestern France have delivered a shock to the regional economy, Finance Minister Roland Lescure said on Monday. The region is one of the centres of French wine production and a major centre for tourism.
"It's like a clap of thunder for an area which could have done without this," Lescure told reporters.
President Emmanuel Macron's government will discuss the wildfire situation at a cabinet meeting on Monday.
Spanish Prime Minister Pedro Sanchez has said his government will on Tuesday declare a civil protection emergency for the central provinces plagued by the wildfires, unlocking additional recovery funding.
More than 150,000 hectares have burned across Spain since January, Sanchez has said, six times the area destroyed during the same period last year. In both Bordeaux and Avila, July high temperatures have averaged 32C, almost 6C above the month's normal high between 1961 and 1990, according to the Reuters Climate Monitor.
The scale of this summer's wildfires in Europe is putting pressure on firefighting resources and raising questions about how to respond.
Under the European Union's civil protection mechanism, Greece and Italy have each sent two Canadair water-bombing aircraft to Spain, while Portugal has deployed more than 100 military personnel along with equipment.
Two more planes were due to arrive from Turkey, the Spanish interior ministry said.
French firefighters were hoping to take advantage of more favourable conditions on Monday before the temperatures rise again to as high as 37C later this week in the Bordeaux area, according to forecasts from France's weather office.
"It's a race against time before the heatwave returns," said Steffe, the mayor of Cestas.
with EFE and DPA
