The woman was climbing with a group of five other people up the north face of the Pointes de Mourti (3,564 metres high) when the group was swept away by a snowslide above Moiry Lake on Saturday morning, Valais cantonal police said.
The avalanche, 150 metres wide and 800 metres long, also killed a 50-year-old Valais man and injured the four other climbers, police said.
The climbers were a little more than 100 metres in altitude below the peak in the Val d'Anniviers region when the incident occurred.
Another climber in the area alerted emergency rescue services, with three helicopters from Air Glaciers responding the scene.
All the victims were residents of the canton of Valais, police said on Sunday.
On Saturday afternoon, another avalanche took the lives of a 28-year-old Swiss woman and a 30-year-old German who were descending from the Zinalrothorn, a mountain near Zermatt.
As they were climbing down they were probably surprised by a large snowslide and carried several hundred metres to the Trift glacier, Valais police said.
Rescue workers from Air Zermatt responded to the scene but the pair were already dead, police said.
The accidents occurred as temperatures rose above 30 degrees in many parts of Switzerland, rising as high as 34.9 degrees in Bad Ragaz in the canton of Saint Gallen and 34.7 degrees in Chur, in the canton of Graubünden, MeteoSwiss, the national weather office reported.
However, a cold front on Sunday brought heavy rain and a sudden drop in temperatures to several regions.
Meanwhile, police reported another weekend fatality in the canton of Valais on Saturday when a 19-year-old motorcyclist from Geneva crashed into a car in Salvan, while driving from Martigny, a few kilometres to the south.
The victim lost control of his motorbike on a curve and collided with a car driven “normally” in the opposite direction by a 54-year-old man, police said.
The victim, a Swiss citizen, died instantly, police added.