Stage 18, the first in the Alps, was led by breakaway riders throughout the stage's climbs, which included the first-category Col de Vars and the hors catégorie Col d'Izoard and Col du Galibier. With remaining of the Galibier, Bernal attacked from within the group of general classification contenders containing Alaphilippe and Thomas, allowing Bernal to recover half a minute on his rivals by the finish and move up to second overall. Around into stage 19, Pinot, who had been placed fifth in the general classification, abandoned the race with a leg muscle injury. At the head of the race in the closing kilometres of the planned second to last climb, the hors catégorie Col de l'Iseran, Bernal attacked from the group of overall contenders, catching and passing final breakaway riders by the summit. Alaphilippe was dropped following Bernal's attack, and was two minutes behind at the summit. During the descent, the race was neutralised when a hailstorm caused ice and landslides to block the route to the final climb to Tignes, particularly a mudslide at the foot of the descent before Val-d'Isère. Times for the general classification were taken at the summit of the Iseran, with the stage victory and most combative rider of the day not awarded. As a result, Bernal, who had been in second place overall, moved ahead of Alaphilippe and took the yellow jersey. The stage was shortened from to .The inclement weather also caused the penultimate stage to be reduced in length beforehand, from to , bypassing the first-category Cormet de Roselend and the second-category Côte de Longefoy, with the only climb being the hors catégorie-rated one to Val Thorens at the finish. A group of 29 riders established a two-and-a-half minute lead over the peloton, before being vastly reduced to six on the early slopes of the Val Thorens climb. With remaining, Nibali attacked from this group and soloed to victory, ten seconds ahead of chasers Landa and Alejandro Valverde. Close behind, Bernal and Thomas led the other general classification contenders Urán, Buchmann and Kruijswijk. Alaphilippe was dropped again, losing three minutes to Bernal and dropping from second overall to fifth. Thomas therefore finished the race in second place overall, 1' 11 down on Bernal.