A good summer forecast for the high mountains is not about sun icons. Every evening before a summit day we check three numbers and one feeling.
The freezing level
If the freezing level stays above 4 000 m all night, the snow does not refreeze. Crevasse bridges get weak and the couloirs start to move. We want a clear night and a freezing level that drops below the route.
Wind at altitude
Thirty kilometres an hour in the valley can be eighty on the Bosses ridge. Above fifty we slow down, above seventy we stay home.
The afternoon storm
Summer storms build in the afternoon, fast. That is why we start at two in the morning and why the turnaround time matters so much.
The feeling
And then there is the sky itself at three in the morning, from the hut door. Some nights the numbers say yes and the stars say wait. We listen to both.
