Alps: a hot day, then the rain rolls in

Chamonix reaches 31°C in the valley today under clear skies. Make the most of it. A front pushes through tomorrow: highs drop to around 26°C with 4 to 5mm of rain across the western Alps, and Zermatt cools to roughly 21°C by Saturday. If you are heading up, take the dry morning and pack a shell for the turn. The heat won't last.