Firefighters on Wednesday struggled to contain fires that have threatened the southern city of Marseille, temporarily shut down the airport and delayed trains.
Marseille mayor Benoit Payan said that while the fire was not yet under control, it was "clearly decreasing".
"We hope that the weather will continue to improve because they are what will allow the fire to be controlled, contained and stopped," Mr Payan told radio FranceInfo.
The mayor also announced the lifting of an overnight lockdown in the city's 16th arrondissement, but "called on all Marseille residents to exercise the utmost caution in the area".
On Tuesday afternoon, Mr Payan warned that fires were "at Marseille's doorstep".
Several forest fires have raged in recent days in southern France, fanning out at speed due to wind and parched vegetation after a heatwave.
Light grey smoke gave the sky over Marseille’s old port a dusty aspect as water-dropping planes tried to extinguish the fire in the outskirts of the city, which has some 900,000 inhabitants.
The fire is still progressing at 1.2km per hour, Eric Brocardi, spokesperson for the national federation of firefighters, told BFMTV. "This is a significant speed for this type of disaster, especially near urban areas."
A number of flights departing from Marseille's international airport were delayed or cancelled after a partial closure on Tuesday. The airport's website indicated that there would be "no restrictions" on flights starting 9.30am CEST but that "disruptions were to be expected".
The website of the SNCF national rail operator showed more than a dozen train trips had been cancelled in and out of the city. It said rail travel to and from Marseille would remain "highly affected" on Wednesday.
The fire started in a vehicle in the area of Pennes-Mirabeau to the north of Marseille, on the road to the airport, roaring across 700 hectares by the evening, firefighters said.
The country must brace for a "high risk summer," Interior Minister Bruno Retailleau warned during a Tuesday evening visit to firefighters in the region.
Some 400 people have been evacuated and 63 houses damaged, with some dozen destroyed, Mr Retailleau said. About 100 people have suffered light injuries, including from emergency services.
"At the moment that I speak to you there are no deaths, which is remarkable given the extent of the fires," Mr Retailleau said.
The fire near Marseille is just the latest to hit France in recent days.
To the West along the Mediterranean coast, near the city of Narbonne, more than 1,000 firefighters from around the country were seeking to contain another blaze.
It had crept across 2,000 hectares (4,900 acres) of trees since starting on the property of a winery on Monday afternoon, emergency services said.
The fire near Narbonne caused authorities to close the A9 motorway to Spain, but on Tuesday morning they said they were progressively reopening it to traffic.
Scientists say human-induced climate change is increasing the intensity, length and frequency of extreme heat that fuels forest fires. Reports have shown that cities in France are expected to reach 50 degrees Celsius during heatwaves by 2050.
The cities of Marseille and Narbonne are also surrounded by poorly maintained highly flammable vegetation. "The state of dryness of vegetation at the beginning of July is very unusual, approaching historical years like 2017," said Meteo France.
Winds are expected to abate by Friday, but Meteo France warned that "the risk of fires starting will remain high even in the absence of wind".
Climate change is not the only reason for an increasing risk of forest fires, said geographer Guillaume Faburel, who pointed at cities expanding on average in France 2.5 times faster than the population growth.
"There is a problem of cohabitation between cities and surrounding areas that have natural spaces which are not maintained as they should be," Mr Faburel told radio RTL. "We have mega fires because we have mega cities."
