Scaling a mountain pass at the right time is the guarantee of a successful day: open road, clear skies and pleasant temperatures. Conversely, setting off too early in the season risks finding a pass that is still closed, and starting too late in the day exposes you to storms. Here is how to choose well when to climb the Oisans mountain passes by bike.
The best season for cycling in the Oisans
The heart of the cycling season runs from June to October. Low and medium-altitude passes such as’Alpe d'Huez, the Col d’Ornon where or Cross of Iron are accessible from spring until late autumn. The month of September, which is often calm and less crowded, is a well-kept secret amongst connoisseurs.
Opening and closing of mountain passes
The giants above 2,000 m follow a shorter schedule, dictated by snow clearance. The Col du Galibier (2,642 m) is generally only open from late May/June to October; its road can close as soon as the first snow falls. The Col du Lautaret, on a major road, remains clear for much longer. Dead-end roads such as the Col du Sabot Where is the Lake Besson climb mostly in the middle of summer. Always check whether it is open from tourist information offices or road services before setting off.
Dealing with mountain weather
At high altitudes, the weather changes quickly. A few useful reference points:
- Thunderstorms These often form in the late afternoon during the summer: it’s best to set off in the morning for long climbs.
- The heat in the valley can be intense: on south-facing slopes as Oulles, set off early and take plenty of water.
- The cold and the wind Be on your guard at the summit, even in July: a windbreaker is essential for the descents from the Galibier or the Lautaret, where the temperature can drop by 15 °C.
Adjust one's schedule to the exit
For a big stage like the Galibier from Bourg-d’Oisans, set off in the freshness of the morning: you'll avoid the heat of the valley on the way up and enjoy superb light. For a short and explosive climb, a slot at the end of the day, once the heat has dropped, can be ideal.
Dressing for the season
In spring and autumn, make sure you pack warm clothes for the descents and the still-chilly summits. In the height of summer, focus on sun protection, a breathable base layer and plenty of water. Whatever the season, a lightweight windbreaker remains your best friend in the mountains.
The weather reflex at the summit
Because conditions can vary drastically between the foot and the summit of a pass, each of our fact sheets includes a section on live weather which displays the temperature, wind and its direction, both at start and at the summit. A quick check before each trip can save you a lot of unpleasant surprises. To find out more, take a look at our guide which mountain pass to climb according to your level.
Frequently asked questions
When is the Col du Galibier open?
Usually from late May/June to October, depending on snow clearance. Check opening times before you set off: it can snow even in summer.
What is the best month for cycling over the Oisans mountain passes?
June to September offer the best conditions. September is often stable, mild and calmer.
Is it cold at the top of the mountain passes in summer?
Yes: above 2,000 m, the temperature drops significantly and the wind makes it feel even colder. Always take a windbreaker with you.
Plan your climbs with confidence thanks to the detailed guides in the Oisans mountain passes page, including weather conditions at the summit, the route profile and the GPX track.