This has in turn meant authorities have urged climbers to delay scaling the mountain, which straddles the French-Italian border, because high temperatures have created dangerous conditions.
"The heat wave has also an impact on high mountains, it doesn't stop on the plains," said Nicolas Zickler, commanding officer of a high mountain police rescue team.
"The routes have changed, the timing of the season has changed, the weather conditions have changed," she said.
"The decrease of the glaciers is worrying," said the president of Mont Blanc guide company Compagnie des Guides de Chamonix, Olivier Greber.
Reporting by Cecile Mantovani, Denis Balibouse, Writing by Charlotte Van Campenhout; Editing by Chris ReeseOur Standards: The Thomson Reuters Trust Principles.
Persons:
Mat Cooper, Daniel Trevena, Les Cosmiques, Denis Balibouse, Nicolas Zickler, Cooper, Mont, Olivier Greber, It's, Cecile Mantovani, Charlotte Van Campenhout, Chris Reese
Organizations:
REUTERS, Compagnie des Guides de Chamonix, Thomson
Locations:
Chamonix, France, Blanc, CHAMONIX, Mont Blanc, Australian, Swiss, Blanc's