Amid sweltering heat, firefighters in France battle wildfires that have forced thousands to evacuate.

French firefighters were battling two gigantic wildfires on Monday that have torn through 55 square miles of dry pine forest in southwestern France over the past week and forced about 16,000 people to evacuate.

Roughly 1,700 firefighters from around France have been deployed across the Gironde region, a coastal area around Bordeaux, to try to contain the raging flames. About a dozen have been lightly injured.

“We’ve never experienced two fires of this size in a same department,” Marc Vermeulen, a fire chief in Gironde, told Franceinfo radio on Monday, adding that firefighters were also having to stop 20 or so new blazes from starting every day.

Dark plumes of smoke filled the sky as water-bombing planes buzzed overhead on Monday, flying back and forth to dip into ocean and fill their tanks with water to fight the two blazes.

The fires have not caused any deaths and have caused only minimal damage to buildings.

But local authorities were bracing for the worst on Monday, as a heat wave is expected to hit with full force, and they announced evacuation orders for an additional 8,000 people from towns that were in the line of the fire.

“The situation is critical, mainly because the weather is unfavorable to us,” Vincent Ferrier, a local official in Langon, an area of Gironde, told reporters on Monday.

Mr. Ferrier ticked off several things working against the firefighters: the record-breaking temperatures that were expected in the area, a lack of humidity and strong, shifting winds that have thwarted firefighters’ attempts to contain the flames and that could start secondary fires by blowing embers into parched patches of forest.

“This is a fire that continues to spread,” he said. “We have to constantly adjust.”

One of the fires was concentrated near La Teste-de-Buch, south of the bay of Arcachon, a popular vacation destination with sandy beaches and dozens of campsites popular with tourists in the summer.

Many vacationers have been forced to evacuate over the past few days. Fifty people slept in temporary shelters that had been set up in gymnasiums or recreational centers overnight, local authorities said Monday.

The second blaze, located further inland, near Landiras, has left burned tree trunks and scorched earth in its wake.