Alps: the freezing level drops 2,000 metres by Wednesday

Two warm days, then a hard turn. Chamonix peaks at 23C on Tuesday with the freezing level near 4,700 metres, so high routes stay dry and clear. Wednesday brings thunderstorms, 15 mm of rain and a freezing level collapsing to roughly 2,750 metres by evening. Above 3,000 metres that means fresh snow on rock overnight. Take the big day on Tuesday.