Western Alps: first cold snap of late summer

A sharp cool-down is moving through the western Alps this week. Chamonix falls from 22°C today to 17°C by Friday, with nearly 60 millimetres of rain arriving first. Zermatt's overnight lows slide towards 5°C in the valley, colder still higher up. The freezing level is dropping fast. Above 3,000 metres, expect the first fresh snow on the summits, so pack a warm layer and check the forecast before any glacier crossing.