Zermatt sat at 3.8 °C at dawn today and should reach about 17 °C by afternoon. No rain is forecast through Thursday, and Chamonix looks just as dry. That is a 13-degree gap between your first step and lunch. Start in a fleece and plan to stow it. Up in Tromsø it is already below zero this morning, with drizzle due from tomorrow.
Fleeces ↗