Quick reads. Lasting takeaways.
High summer is loosening its grip on the western Alps. Chamonix touches 28 degrees this afternoon, then tomorrow's high falls to 19. That is a nine-degree drop overnight. Valley mornings already sit near 13 degrees, and it stays colder the higher you climb. A light windproof shell over a merino base covers both ends of the day, without the weight of a midlayer you would carry unused past noon.
Merino base layers ↗Late-summer heat is on its way out. Chamonix hits 29°C today, then a front rolls in on Friday with roughly 15mm of rain. By Saturday the valley tops out near 18°C, and at Zermatt's altitude the overnight low drops to about 7°C. The freezing level falls with it. Pack a warm layer even for a fair-weather summit, and check the forecast again before committing to a high route.
Insulated midlayers ↗The Alps get one more warm day before the weekend breaks. Chamonix peaks near 29 degrees on Thursday, then Friday's front drops highs back to 21 and brings roughly 14mm of rain. Higher up the swing is sharper. Zermatt at 1,600 metres falls from 24 to 17 degrees in a single day. Pack the shell now. A bright Thursday morning tells you nothing about Friday's ridgeline.
Waterproof shells ↗Chamonix takes nearly 19mm of rain today before the front clears. From Wednesday it turns dry and warm, with valley highs climbing toward 30 degrees by midweek. Higher up at Zermatt it stays cooler, around 19 degrees. Pack for both. A packable waterproof covers this morning; a light merino base layer carries you through the warm afternoons that follow.
Packable waterproof jackets ↗The first autumn signal is already showing at altitude. Zermatt sat at nine degrees this morning at 1,600 metres, yet the afternoon still climbs past twenty. That is a twelve-degree swing before lunch. A merino base layer plus a packable wind shell covers both ends, without the bulky midlayer you would carry unused all day. Start cold, warm up moving.
Merino base layers ↗High summer is loosening its grip on the Alps. At 1,600 metres around Zermatt, mornings start near 8°C, while the valleys push past 24°C by mid-afternoon. That is a swing worth dressing for. A merino base layer under a light windproof handles both ends, without the bulk of a midlayer you carry unused all day. One thing to plan around: a front rolls in on the 25th, with 7 to 8 mm of rain forecast for Chamonix and Zermatt. Go early in the window.
Merino base layers ↗A dry window opens over the western Alps on Sunday. Chamonix and Zermatt both stay rain-free before showers return on Monday. The catch is the swing. Mornings sit near 8 to 9 degrees, afternoons climb past 20, roughly a 15-degree spread in one day. Start colder than feels comfortable, then shed layers as the valley warms. A merino base under a light shell handles both ends.
Merino base layers ↗Chamonix takes the brunt today, with around 32 millimetres of rain before the front clears. Then it settles. Two dry days climbing towards 22 degrees. The catch is the nights: Zermatt drops to 6 degrees after dark, a wide swing from the afternoon warmth. Pack for both ends. A merino base layer covers the cold dawn without weighing down the midday climb.
Merino base layers ↗A sharp cool-down is moving through the western Alps this week. Chamonix falls from 22°C today to 17°C by Friday, with nearly 60 millimetres of rain arriving first. Zermatt's overnight lows slide towards 5°C in the valley, colder still higher up. The freezing level is dropping fast. Above 3,000 metres, expect the first fresh snow on the summits, so pack a warm layer and check the forecast before any glacier crossing.
Fleece midlayers ↗Chamonix touches 29 degrees today under near-clear skies. Then the weather breaks. Tomorrow the high drops to 21 with almost 30mm of rain, the day after to 16 and still wet. Zermatt runs the same line, from 24 down to 17 in a single day. Heading up high? Today is the window. Pack a proper shell, because the swing lands fast.
Hardshell jackets ↗High summer still holds across the western Alps today. Chamonix reaches 24°C, Zermatt around 22°C, both under thin cloud. Make the most of it. By the third day the pattern breaks: Chamonix drops to 19°C with roughly 11 mm of rain, Zermatt to 17°C. Plan the long ridge for the next two days and keep a hardshell in the top of the rucksack for the turn.
Hardshell jackets ↗A soggy start to the week clears fast. Chamonix takes nearly 40 millimetres of rain today, then dries out completely on Tuesday and Wednesday. Highs climb from 21 to 26 degrees across those three days, with Zermatt a touch cooler at altitude. Wait it out. The midweek window is the one to plan for: dry trails, firmer ground underfoot and afternoon warmth, without the storm risk hanging over the valleys today.
Waterproof jackets ↗Chamonix reaches 28 degrees today, then falls to 19 by tomorrow. Eight degrees in a day. Heavy rain moves through the valley first, and higher up around Zermatt afternoons settle near 17 degrees. The warm spell is closing for now. If you are heading into the Western Alps over the next few days, pack a proper hardshell, not just a windproof layer.
Hardshell jackets ↗Chamonix reaches 28°C today under near-clear skies. Rain moves in on Sunday, and by Monday the high drops to 21. Zermatt cools harder still, from 23°C down to 16 across the same three days. Take the exposed ridges now. Anyone heading up midweek wants a shell and a warm layer packed, not just the kit that feels right this afternoon.
Hardshell jackets ↗Chamonix and Zermatt both sit dry and warm today, near 28°C down in the valley. That window is short. A wet front moves in over the weekend, with around 6 mm of rain forecast for Saturday and closer to 9 mm on Sunday. If you have one big walk planned this week, take it today. For Saturday and Sunday, a packable waterproof earns its place in the rucksack.
Waterproof shell jackets ↗Zermatt at 1,600 metres sits near 26°C this afternoon, and Chamonix runs warmer still down in the valley. Make the most of it. From Thursday a change moves through: highs in Zermatt slide towards 19°C by Friday, with roughly 3mm of rain. Mornings at altitude already start near 14°C. If you are up for two or three days, pack the shell you would otherwise leave behind.
Hardshell jackets ↗Warm, calm mornings this week give way to building afternoons in the high Alps. Chamonix reaches 28 degrees today, then 18 millimetres of rain arrive on Thursday; Zermatt holds clear until Friday. That is the textbook August rhythm: storms gather fast over the massifs from around two o'clock, and above the tree line there is nowhere to shelter. Be over your highest pass by early afternoon. Start early.
Waterproof shell jackets ↗Chamonix climbs past 26°C this week under clear skies. Tromso sits near 10°C at the same moment, with drizzle and a 23 km/h wind off the fjord. Same continent, same week. If your summer trek heads to Arctic Norway rather than the Alps, pack for autumn: a waterproof shell, a warm midlayer, gloves you would leave at home in Chamonix. The rain holds — Wednesday drops over 20mm on Tromso.
Waterproof jackets ↗High summer has the Alpine valleys baking. Chamonix climbs towards 28°C by afternoon this week, and that heat sits on you through the first few hundred metres of any climb. Start at first light. Drink before you feel thirsty, and refill at every fountain you pass. By the time the valley peaks, you want to be on the ridge, not still grinding up the switchbacks. Carry more water than feels sensible.
Drinking bottles ↗The Western Alps are running hot. Chamonix sits near 28 degrees in the valley today and tomorrow, and even Zermatt at 1,600 metres climbs into the mid-twenties. Then it breaks. Tuesday brings rain and a drop of five to six degrees across both. Start your climbs early while the heat holds, and pack a light shell for the back half of the week.
Lightweight rain jackets ↗
