PARIS — Southwest France sweltered on Monday as temperatures rose to 43 degrees Celsius in parts of Charente and Aude, prompting the country's highest heat alert across a dozen departments.

In Aude, where vineyards and Mediterranean scrub stretch across hills, hundreds of firefighters remained on the ground to monitor the perimeter of a vast wildfire that burned through 160 square kilometres last week.

Local authorities said the blaze is now contained, but warned it could smoulder for weeks, with hot spots still posing a risk.

Meteo-France, the country's national weather service, placed 12 departments on red alert, a designation issued only eight times since its creation in 2004 following a deadly summer heatwave the year before.

Officials said the red alert allows local authorities to cancel outdoor gatherings, shut public spaces and modify school or summer camp timetables.

The warning is triggered for extreme, prolonged heat events which pose severe health risks and the potential to disrupt daily life.

Social media posts showed shuttered streets in Valence, residents covering windows with foil to reflect sunlight and tourists sheltering under umbrellas along the Garonne in Toulouse. Café terraces in the south were empty as people moved indoors to escape the heat.

The heatwave, France's second this summer, began on Friday and is forecast to last all week, extending into the 15 August holiday weekend.

Forecasters expect it to push north, with highs of 38°C in the Centre-Val de Loire region and up to 34°C in Paris.

According to local media, the conditions are also worsening air quality, prompting pollution alerts in several regions.

In Provence-Alpes-Côte d’Azur, the prefecture has declared an ozone pollution emergency across several departments, introducing restricted traffic measures in parts of the Aix-Marseille-Provence area to cut emissions.

Paris is facing similarly poor air quality, according to the weather monitoring agency Airparif, which also flagged degraded conditions in major cities.

Health officials have warned residents to avoid outdoor activity during peak pollution and to limit unnecessary driving. — BBC