Firefighters in France are working around the clock to contain wildfires that have been raging in the Gironde region, while bracing for another sharp rise in temperatures.

“The fire is like David against Goliath,” said Eric Brocardi, spokesman of the national firefighters’ federation.

Four of his colleagues had died in recent weeks across France, he said, and 2,000 had been deployed in the Gironde to contain the flames, which for days have ravaged the countryside between the coastline and Bordeaux.

According to regional prefect Sophie Brocas 14 places that had already been hit by the fires saw new flare-ups on Tuesday. “We are not in the clear,” she said.

This summer’s fourth heatwave was expected to start by Wednesday, bringing temperatures in the area to 40C.

Similar temperatures are expected in Spain.

Dozens of communities are still threatened by wildfires that forced more than 70,000 to evacuate their homes over the last week – although many have now been allowed back.

The Madrid region has been especially affected, but Prime Minister Pedro Sánchez said while there were highly challenging hours and days ahead, light was beginning to appear “at the end of the tunnel”.

In neighbouring Portugal, 400 firefighters were tackling a large fire on three active fronts in the eastern Guarda area.

The French city of Bordeaux, which has a population of 260,000, is not currently under threat, according to officials, despite the fact that one of the wildfires burning on Monday came only 15km (9 miles) from the city’s periphery.

But Commander Rémi Lassoureille, who is leading the firefighting response in the Gironde region, is still worried about the western edge of the wildfire.

“We are frightened about the impact on Bordeaux and the metropolitan area,” he said. Air quality in the city also deteriorated greatly.

“By Sunday evening everything had really begun to empty out,” a holidaymaker from Essex told the BBC, adding that the air was “really smoky” with bits of ash. “People were staying indoors, so it was eerie, and very sad.”

The majority of residents and tourists were wearing masks and the smell of smoke clung on to clothes for days, she said.

A firefighter “got a round of applause” as he walked through the Marché des Chartrons in Bordeaux where restaurants were having to close their doors because of the ash in the air, she added.

“The city has been very quiet,” said Graham White, president of the Bordeaux British Community. “The shops, restaurants and cafes are fairly empty… Interestingly on Sunday when there was still smoke, there were people brave enough to sit outside on terraces.”

White, who has been living in the area for several years, said this sort of event was “something significant”.

But some news reports had suggested the situation in Bordeaux was “akin to being the next Great Fire of London”, which was not the case, White added.

Health Minister Stéphanie Rist said the government was being “very vigilant” in terms of air pollution and urged people in the affected areas to stay indoors.

On Tuesday morning the Gironde prefect ordered a new evacuation of all camping sites near the coast at Lacanau, while those in the nearby town were allowed to stay put but told to prepare for sudden evacuation.

About 4,000 tourists told to leave the area are in addition to the 220,000 people evacuated around France in recent days.

An estimated 240 homes and houses have been destroyed, officials have said.

By midday on Tuesday firefighters were already intervening in various parts of the region to tackle fires that were picking up again.

A 23-year-old man who was arrested on suspicion of starting a fire in the Var region. is now facing 15 years’ imprisonment. Interior Minister Laurent Nuñez said that 184 people had been arrested since 6 July in connection with the fires.

Peggy Plouhinec, the general director of Château Picque Caillou – one of the few wine estates on the west side of Bordeaux – told the BBC that her business chose to close at the weekend because of the smoke, but that the situation had improved since then and that a bout of rain on Sunday night had helped.

While her vineyards were not at risk, she said tourists had “deserted” the region.

“The hospitality sector will be impacted this summer, that’s for sure,” she added. “What is happening is unprecedented. We’re lucky that we haven’t been too affected yet, but the business will still suffer from the lower numbers of tourists.”

“But many people have lost their homes or their businesses, not to mention the firefighters who have been hard at work for weeks now and who must be exhausted.”

One resident of Cap Ferret, which was evacuated late last week, told French media that his main concern now was for the peninsula he lived in, rather than the big city city inland.

“Everyone talks about saving Bordeaux, but in Bordeaux there’s nothing but concrete. Have you ever seen concrete burn?”

“Here, there are only trees… and when you see all that has burned, it’s a catastrophe.”

Additional reporting by Xavier Pallas