LEGE-CAP FERRET, France (AP) — Firefighters in southwest France battled an uncontained wildfire four times the size of Paris on Wednesday as temperatures were forecast to reach 40 C (104 F), threatening to turn a calm night into only a brief reprieve.

Authorities in the Gironde region said the blaze had not spread overnight, but rising heat and afternoon winds could revive smoldering hot spots, carry embers across firebreaks and open new fronts beyond crews’ reach.

At the command center in Lège, firefighters bent over maps spread across a car hood, tracking three danger zones: northern Cap-Ferret; the wooded corridor around Marcheprime, Cestas and Saint-Jean-d’Illac; and a military site near Martignas, where a major outbreak forced a large deployment.

More than 2,200 firefighters and over 20 aircraft remained mobilized, backed by crews from across France and European partners.

“We strike quickly and strike hard at any new smoke emissions,” Gironde fire commander Matthieu Jomain said.

Wednesday expected to be the week's hottest, driest day

The advance of major fires in the Landes and Var regions have been halted. That left Gironde as France’s biggest remaining wildfire battle, Interior Minister Laurent Nuñez said.

The Gironde fire forced 220,000 people to flee at the peak of the crisis. Tens of thousands have since been allowed home, but authorities warned that the danger had not passed.

Extreme heat strips moisture from vegetation and drives down humidity, turning grasses, brush and forest litter into faster-burning fuel.

Météo-France said Wednesday would be the hottest and driest day of the week, with elevated wildfire danger across every region of France. Drought now covers mainland France and Corsica, with soils nearing the record dryness reached in August 2022.

Smoke from the Gironde and Landes fires also pushed particulate pollution higher across both departments, regional air-quality monitors said.

Gironde authorities ordered 4,000 more people out of tourist sites along the Atlantic coast on Tuesday, widening what may be France’s largest peacetime evacuation.

“The situation remains complicated. That’s clear. We’re not out of the woods,” said Gironde prefect Sophie Brocas, who also authorized 60,000 evacuees to return to three Bordeaux suburbs untouched by fire.

The opposing movements — thousands ordered out of coastal resorts as others returned with mobile phones on and emergency bags packed — captured how precarious the situation remains.

The disruption was spreading beyond the burn zone into Bordeaux’s peak tourism season.

Edouard le Grix de la Salle, who runs Château du Grand Verdus with his brother, said official appeals to avoid the region threatened its wine-tourism trade. “How did they not think about protecting that sector?” he told The Associated Press.

Tens of thousands begin returning home in Spain

At the height of the crisis, roughly 330,000 people were driven from homes and vacation sites across France and Spain.

Tens of thousands of people began returning home in central Spain after firefighters made progress around Madrid and Ávila. Evacuation orders were lifted for about 20,000 people in the Madrid region, while stay-at-home restrictions ended for another 14,000.

But 10,000 people remain under evacuation orders in Castellón, where a fire was still out of control as Spain braced for its fourth heat wave of the summer.

At one point the Gironde blaze created a black thundercloud, electrified and lit from within, that generated lightning, violent winds and new fires beyond the original front. The pyrocumulonimbus was the first recorded in France.

More than 1,160 square kilometers (448 square miles) have burned across France this year, according to the Interior Ministry.

Europe is the world’s fastest-warming continent, warming at more than twice the global average, according to the European Union’s Copernicus climate service. Western Europe recorded its hottest June on record, with extreme heat and widespread dryness contributing to the spread and intensification of fires in France and Spain, Copernicus said.

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Adamson reported from Paris. Suman Naishadham in Madrid and John Leicester and Masha Macpherson in Paris contributed.