✦ At a glance
- At altitude, temperature drops by roughly 6°C every 1,000 m: above 1,500 m, it’s 10 to 15°C cooler than down in the valley.
- The Northern Alps are full of lakes, streams and natural swimming spots accessible from GSI’s resorts.
- Hiking, mountain biking, via ferrata, open-air pools, festivals: a mountain summer has nothing to envy from the seaside.
- GSI by Foncia offers apartments and chalets available to rent from July across 17 destinations.
Why the mountains are the ideal heatwave escape
While thermometers in Lyon, Grenoble or Paris push past 38°C, fans run non-stop and asphalt ripples in the heat, the Northern Alps remain a pocket of coolness less than 3 hours’ drive for most of France.
The mountains aren’t just a winter destination. Every summer they draw thousands of families, couples and outdoor enthusiasts in search of what neither the sea nor the city can offer in July and August: crisp air, open landscapes, the sound of a mountain stream, and nights where you genuinely sleep under a duvet.
Beyond the thermal comfort, a mountain summer also brings a freedom of movement that’s hard to find elsewhere: no queues on the trails, mountain huts still serving cheese-topped crusty bread, lakes where you can dive in without fighting for a patch of towel space. And an evening light over the ridgelines that rivals any Mediterranean sunset.
GSI by Foncia operates across 17 destinations in the Northern Alps, spread between Savoie, Haute-Savoie and Isère. From family-friendly resorts to premium addresses, each one offers a genuine alternative to the lowland heatwave this summer.
Cool by the numbers: what altitude really changes
Altitude changes more than just the temperature. It transforms air quality, light, humidity, and even your body’s rhythm. In the mountains the air is drier, carries fewer fine particles, and the slightly reduced atmospheric pressure brings a noticeable muscular relaxation after 48 hours on site.
GSI’s resorts sit between 900 m and 2,100 m depending on the area, which guarantees daytime temperatures around 18 to 24°C in peak summer, and cool nights between 8 and 14°C. Numbers that make all the difference when urban heat islands struggle to drop below 25°C even at 2 a.m.
In practice, this changes everything about a holiday routine: you can hike in the morning without suffering from the heat, swim in a mountain lake in the afternoon, and end the evening with a blanket over your knees on the terrace. It’s this contrast with everyday heatwave life that makes a mountain stay so memorable.
📐 What altitude actually changes
- Temperature: -6°C for every 1,000 m of elevation
- Guaranteed cool nights (a duvet is essential even in August)
- Cleaner air, fewer urban allergens
- Stronger UV: sunscreen is essential even on overcast days
- Hydration: drink more than at lowland altitude even without feeling thirsty
- Light acclimatisation: plan a quieter first day if you’re heading above 2,000 m
Swimming and cool-down spots by GSI destination
Every resort in the GSI network has its own watery treasures: natural lakes, open-air pools, streams within walking distance, and wellness areas with heated pools. Here’s a tour of the best places to cool off.
Alpe d’Huez
1,860 m
Lac Besson, accessible on foot or by bike from the resort, offers crystal-clear swimming facing the glaciers. The Aqua’ludique Centre offers an indoor pool and relaxation areas for cooler days.
Méribel
1,450 m
The Tuéda Nature Reserve, in Méribel-Mottaret, shelters a crystal-clear lake surrounded by centuries-old larch trees. A protected setting, turquoise water, a quiet and exclusive feel. Méribel’s sports centre has a pool open during summer.
Megève
1,113 m
Megève in summer means strolling through a postcard-perfect village facing Mont Blanc, with Lac de Combloux just a few kilometres away for a swim. Megève’s open-air municipal pool offers a clear view of the surrounding peaks.
Le Grand-Bornand
934 m
The most photographed village in the Aravis range comes alive in summer along the Borne, a clear stream where children love to play. The Grand-Bornand’s open-air pool is a summer classic. And in August, the “Au Bonheur des Mômes” festival turns the destination into a giant playground for families.
Les Saisies
1,650 m
The highest resort in the Beaufortain, Les Saisies offers an open plateau facing Mont Blanc, with temperatures rarely climbing above 20°C in peak July. The natural cool air at 1,650 m is the number one argument during a heatwave. A short drive down towards Beaufort opens up a spectacular lake-studded territory (see the Saisies & Beaufortain box below).
La Plagne
1,800 m
Averaging 1,800 m, La Plagne stays cool all summer long. In summer, the Bellecôte glacier offers guided glacier hiking experiences. Lower down, the villages of Montchavin and Les Coches give access to streams and clearings ideal for a cool-down break.
Les Arcs
1,600 m
Les Arcs is reached in minutes from Bourg-Saint-Maurice via the Arcosal, Europe’s fastest funicular. Once up there, the massif offers mountain bike routes for every level, and Lac de Roselend (at 1,557 m) remains a go-to swimming spot in the region.
Valmorel
1,400 m
Valmorel is one of the rare alpine resorts with a fully pedestrian village centre. In summer, this creates a rare strolling atmosphere, with walks through larch forests, the Morel stream within easy reach, and panoramas over the Tarentaise that reward hikers.
Praz-sur-Arly
1,036 m
A village in the Val d’Arly between Megève and Flumet, Praz-sur-Arly has two swimming spots within easy reach. The Les Belles swimming lake (Praz Lac Aventures) offers a supervised swimming area larger than an Olympic pool, with a water park and paddleboarding facing Mont-Charvin. Five minutes away by car, the Flumet swimming lake (l’Arrondine) rounds out the offer with cool water, children’s play areas and a mountain-beach atmosphere that’s very popular in July and August.
Flumet (Val d’Arly)
900 m
The Arrondine swimming lake in Flumet is a Val d’Arly favourite. The water here is genuinely cool, making it an ideal spot during a heatwave. A landscaped green setting with a grassy beach, children’s play area, picnic tables, snack bar and restaurant on site. Lifeguard-supervised swimming from 15 May to 30 September (active supervision 12pm-6pm in July-August). Entirely free to access.
Les Saisies & Beaufortain
1,650 m
From Les Saisies, a short descent towards Beaufort opens up an exceptional lake-studded landscape. Lac de Roselend (1,560 m, turquoise waters) and Lac de Saint-Guérin with its 83 m Himalayan-style suspension bridge are absolute must-sees for views and photography. Note: swimming there is officially prohibited, but kayaking and stand-up paddleboarding are organised by Mountain Sup in Saint-Guérin. The Marcôt swimming spot (Arêches-Beaufort) offers a grassy area for picnics in a calm setting. And of course, a stop at the Beaufort cheese dairy is a must.
Champagny-en-Vanoise
1,250 m
Champagny-en-Vanoise, the gateway to the Vanoise National Park, is an exceptional destination for anyone wanting to immerse themselves in unspoiled nature. High-altitude routes give access to wild glacial lakes, and the valley’s streams are particularly numerous.
What you actually do in a resort in summer
A mountain summer is far from limited to hiking. Alpine resorts have considerably broadened their summer offering in recent years, with activity programmes that rival the best seaside destinations.
🚵 Mountain biking and downhill
Most GSI resorts keep their lifts running in summer for mountain bikers. La Plagne, Les Arcs, Alpe d’Huez and Méribel have bike parks with marked downhill trails for every level. The lifts let you climb effortlessly, ready to descend into the coolness of the woods.
🥾 Hiking and high-mountain routes
The Northern Alps’ trail networks span several thousand kilometres. From pushchair-friendly walking paths to serious high-altitude routes for experienced mountaineers, every resort offers itineraries suited to all levels. Champagny-en-Vanoise and Les Saisies stand out for the richness of their trails exploring alpine environments.
🧗 Via ferrata and thrills
Alpe d’Huez has a well-known via ferrata in the Roche Merle area. Around Les Arcs, particularly in Villaroger, you’ll also find family-friendly via ferrata routes. These activities, best enjoyed in the morning before the heat sets in, combine physical effort with full immersion in the rock.
🏊 Open-air pools and wellness
Several properties in the GSI portfolio have pools, some heated, with terrace access and mountain views. Le Grand-Bornand, Megève and Méribel have public aquatic centres open in season. For wellness-focused stays, certain GSI by Foncia properties include a spa and jacuzzi as part of their amenities.
🎉 Festivals and summer events
A mountain summer also means a rich cultural and festive life. Le Grand-Bornand hosts the “Au Bonheur des Mômes” festival in August, one of Europe’s largest children’s performance festivals. Megève and Méribel bring their villages to life with concerts, craft markets and gastronomic events throughout the summer.
🐄 Discovering alpine heritage
Walks to meet herds grazing in alpine pastures, visits to artisan cheese dairies (notably around Beaufort and Les Saisies), mountain museums, perched rural chapels: summer is the ideal season to truly understand what the mountains are about, far from the winter crowds.
Which destination should you choose for your trip?
👨👩👧👦 Families with children
- Le Grand-Bornand: “Au Bonheur des Mômes” festival in August, pool, stream, lively village
- La Plagne / Les Coches: Famille Plus-certified resort, secure spaces, summer lifts
- Valmorel: car-free pedestrian centre, ideal for young children
- Les Saisies: open plateau, great freedom of movement, Mont Blanc panorama
👫 Couples seeking calm and premium comfort
- Megève: elegant village, gastronomy, spa, alpine art de vivre facing Mont Blanc
- Méribel: warm architecture, Tuéda nature reserve, exclusive feel
- Champagny-en-Vanoise: gateway to the Vanoise Park, glacial lakes, exceptional hiking
- Praz-sur-Arly: unspoiled village, total calm, easy access to Megève
⚡ Sports lovers and thrill-seekers
- Alpe d’Huez: cycling mecca, via ferrata, bike park, mountain lake
- Les Arcs: reference bike park, high-mountain access, funicular for easy ascent
- La Plagne: summer bobsleigh, glacier hikes, downhill mountain biking
- Méribel-Mottaret: direct access to the 3 Valleys trails, heart of the domain
Practical tips to prepare your heatwave escape
Heading to the mountains during a heatwave calls for a few adjustments compared to a typical trip. The goal: make the most of the cool air while avoiding the pitfalls linked to altitude change and the intensity of sun exposure at height.
✈️ Pre-departure checklist
- Book early: July-August is peak season, and the best rentals go fast
- Pack warm clothing for the evenings (a fleece layer is essential even in August)
- Sunscreen SPF 50+: UV is stronger at altitude, even under hazy skies
- Good walking shoes: the trails call for at least basic gear
- Check which activities are open on your travel dates (some lifts run seasonally)
- Check with local tourist offices for trail conditions and events
- Bring a refillable bottle: mountain fountain water is often drinkable, and staying hydrated is crucial
On the logistics side, GSI by Foncia rentals come with à la carte services (linen, end-of-stay cleaning, technical assistance) that make organising a trip considerably easier. Several properties offer full hotel-style services for those who want to relax without dealing with day-to-day hassles.
Worth noting: GSI by Foncia currently offers up to 20% off a selection of properties and destinations for summer stays, with early-booking deals valid throughout July and August. An opportunity not to miss if you’re planning your heatwave escape.
Find your alpine refuge this summer
Over 2,000 apartments and chalets available across 17 destinations in the Northern Alps. Book online, best price guaranteed, flexible cancellation.
Up to 20% off a selection of July-August stays (see conditions on the site)
Frequently asked questions about mountain summers
Is it really cooler in the mountains during a heatwave?
Yes, very significantly so. The standard thermal gradient in the mountains is around -6°C per 1,000 m of elevation. At 1,800 m (the average altitude of alpine resorts), the temperature is therefore 10 to 12°C lower than in the lowlands. During a heatwave reaching 38°C in the valley, a resort like La Plagne or Les Arcs typically sees between 20 and 24°C during the day, with cool nights between 10 and 15°C. The air is also less humid, which makes any residual heat far more bearable than in a city.
Can you swim in mountain lakes?
Yes, many alpine lakes are open for swimming. The water is, naturally, cool (often between 15 and 22°C in peak summer depending on altitude), which is exactly the appeal during a heatwave. Some lakes are lifeguard-supervised in peak season; others are natural sites with no supervision, requiring caution, especially with children. It’s important to check with local tourist offices about authorised and supervised swimming areas before diving in.
Do the ski lifts operate in summer at GSI resorts?
Some ski lifts remain open in summer, mainly for hikers and mountain bikers. Conditions vary by resort and by year. La Plagne, Les Arcs, Alpe d’Huez and Méribel notably offer chairlift or gondola access during the summer season. It’s best to check directly with each tourist office or on the ski area’s website for the summer lift opening dates before planning your stay.
What’s the best time for a summer stay at GSI resorts?
July and August are peak summer months, with the maximum number of activities, events and services available. Early July often offers excellent value before school holidays begin, while August is livelier, particularly for families. The period from mid-June to late September (GSI offers a 10% discount on stays from 13 June to 26 September) is ideal for quieter trips with full access to trails and nature, often at more attractive rates than during peak school holidays.
Are GSI by Foncia rentals available for short summer stays?
GSI by Foncia offers rentals from just a few nights, with conditions varying by property and period. For a refreshing weekend or a full week, the online platform lets you filter availability by your dates. Promotional rates (up to 20% off certain summer stays) generally apply from 5 or 7 nights. For short 2-3 night stays, availability can still be found, particularly outside school holiday weeks.
Are there any particular risks to watch for in the mountains during a heatwave?
Mountain travel during a heatwave comes with a few specifics to plan for. UV radiation is stronger at altitude, even under overcast or slightly hazy skies: SPF 50+ sunscreen is essential. Storm instability is also more pronounced in the mountains in summer: storms can form quickly in early afternoon, so plan to be off the ridges before 2 p.m. on risky days (check Météo-France each morning). Finally, even though the heat is milder, physical exertion at altitude requires greater hydration than at lower elevation.
Is a mountain summer suitable for people who don’t hike?
Absolutely. GSI by Foncia’s alpine resorts offer far more than hiking: markets, gastronomy, pools, spas, cultural visits, festivals, horse-drawn carriage rides (in Megève), children’s activities, e-bikes, summer luge, via ferrata accessible to all. Villages like Megève, Le Grand-Bornand or Méribel offer a lively resort atmosphere that doesn’t require crampons to enjoy an excellent stay. A mountain summer is, above all, an art of living at your own pace, in an exceptional natural setting and at a temperature that’s finally bearable.
