Friday looks like the best of the next three days in the Valais. Zermatt stays dry, with highs around 18 °C. On Saturday the top temperature there falls to 13 °C. Across the border in Chamonix, Saturday brings thunderstorms and about 6 mm of rain. Plan the long day for Friday. Start early and keep a waterproof jacket in the pack anyway.
Jackets ↗