High-summer heat, even up high

Valley temperatures around Chamonix reach 26°C this week, and even at Zermatt's 1,600 metres the nights barely drop below 14°C. That is warm for altitude. On south-facing trails the sun does the work long before noon, so start early and carry more water than a spring hike would need. A litre every two hours is a sensible floor in this heat. Save the exposed ridgelines for the cooler morning air.