"Following difficult weather and landslides forecast for tomorrow, the route of the 20th stage of the Tour de France has been modified," said a statement by the organisers.
The decision means that the first two climbs have been cut from the schedule and the peloton goes straight to Val Torrens.
"Three mudslides occurred in the descent at Cormet de Roselend," Tour Director Christian Prudhomme told AFP in reference to the opening section of Saturday's planned route.
"One of them has damaged the road conditions and we cannot go there. It's the only possible decision."
He added: "Fresh mudslides are possible - we must take the direct route."
Friday's 19th stage also fell foul of the weather when a hailstorm and a landslide forced an early finish to the run from Saint-Jean-de-Maurienne to Tignes.
That was good news for Egan Bernal who took over the yellow jersey and is tantalisingly close to becoming the first Colombian to win the race.