Summer skiing area is open from mid-June until the end of August. The snow conditions tend to be best earlier in the summer.
It is not uncommon to have fresh snowfall on the glacier in June and July. The Signal 1 blue run is always open at the start of the summer but tends to close in late July or early August. On the other hand, the early season is more popular with ski clubs, so the pistes will be quieter and there will be fewer queues if you come later in the summer season.