Western Alps: 28 degrees today, storms tomorrow

Chamonix reaches 28.5°C this afternoon with barely a drop of rain. Tomorrow the valley falls to 20°C and takes around 30 mm, most of it in thunderstorms. Zermatt follows the same pattern, 23.8°C down to 15.3°C. That is an eight-degree swing overnight. If you are on a hut route, plan Wednesday's descent for the morning: fog is forecast from first light. Source: Open-Meteo, 8 September.