Two dry days left in the western Alps. Zermatt reaches around 16°C today and tomorrow, with barely any wind in the valley. Then it turns. Rain arrives on Wednesday and the daytime high drops to about 10°C, a six-degree fall in a single day. Chamonix follows the same pattern. If a longer route is on your list, Monday and Tuesday are the window. For Wednesday, pack a waterproof shell and one extra warm layer.