Police said three people died in hospital, and another apparently was killed in a fall.
Five others were hospitalised in critical condition. Details on the other five hikers that were part of the group weren't immediately provided.
Police said the climbers were trying to reach the Vignettes hikers' hut at 3157m in the Alps.
Europe has experienced turbulent weather over the past several weeks, with unseasonable spells of hot and cold.
In Germany, firefighters pumped rainwater from basements and clearing flooded road tunnels after a storm swept through parts of western Germany overnight.
Germany's far-west Aachen region was the hardest hit, with rescue services receiving hundreds of calls. Aachen police say nobody was harmed in the storm.
France, Belgium and Luxembourg were also affected by heavy rain and hail - weather that is more often seen during the summer than the spring.
Recent days have seen unseasonably warm weather in parts of western Europe. The storm was moving north towards Denmark.
- AP
