Notre Dame survived a massive fire months ago, but the beloved Paris cathedral is facing a new threat: a heatwave.

The high temperatures bearing down on Europe may be a threat to the ailing building, according to Chief Architect Philippe Villeneuve.

“I am very worried about the heatwave because, as you know, the Cathedral suffered from the fire, the beams coming down, but also the shock from the water from the firefighters. The masonry is saturated with water,” Villeneuve told Reuters on Wednesday.

The fire destroyed the roof of the 850-year-old building and toppled the spire, which was added during a 19th-century renovation.

Investigators believe that the fire started at the centre of the roof and spread out, police sources said in April.

Villeneuve said that sensors were placed in the cathedral after the April 15 fire and that there has not been any movement detected since then.

“What I fear is that the joints or the masonry, as they dry, lose their coherence, their cohesion and their structural qualities and that all of sudden, the vault gives way,” he said.

The vaults have not been accessible since the fire, he added. “As I speak here, the vaults could very well collapse,” Villeneuve said, “because, since April 15, we haven't been able to access the vaults, neither from above nor from underneath.”

The heatwave across Western and Central Europe will bring staggering temperatures to France.

Meteorologists are predicting that it will reach its peak Thursday, with temperatures of 42 degrees C (107.6 Fahrenheit) expected in Paris.

On Tuesday, temperatures reached 41.2 Celsius (106 Fahrenheit) in the southwestern city of Bordeaux, a record for the city. The national weather service, Météo France, put 80 of its 96 regions on high alert.