Season
GR20 weather, month by month
January under snow, July under afternoon storms, September in low golden light: the GR20 changes face every month. Here is what actually awaits you, month by month — conditions, refuges, crowds — and our verdict, with no invented temperatures.
Before you read
Conditions, not degrees
One honest note before we start: no official Météo-France climate normals exist above roughly 1,000–1,500 m in Corsica. The altitude "averages" you read elsewhere are extrapolations — so this page reasons in conditions (snow, storms, heat, crowds, services), not degrees. For a detailed look at choosing your window, Best time for the GR20 remains the reference.
Month by month
The GR20 in January
Winter mountaineering only
In January, the GR20 is not a hiking trail: under snow it becomes a winter mountaineering route that demands crampons, an ice axe and genuine experience of snow-covered terrain. The refuges stay open but unstaffed — no warden, no meals, no bookings. The trail is virtually deserted, days are short and rescue takes longer to reach you. Only self-sufficient, experienced alpinists should consider even partial sections. One honest note: Météo-France publishes no official climate normals above roughly 1,000–1,500 m in Corsica, so we publish no altitude temperature figures here. For most hikers, January is the month for planning, not for setting out.
Tip · Use January to book your summer refuges: the Park's booking platform has been open since 20 January 2026.
Month by month
The GR20 in February
Deep winter, experts only
February is the heart of the Corsican winter at altitude: deep snow on the ridges, high passes turned into mountaineering terrain, and the hazards that come with snow-loaded slopes. In winter conditions the GR20 is a mountaineering objective, not a hike — specialist equipment and solid experience are mandatory. The refuges remain unstaffed: no warden, no meals, no resupply. You will meet almost no one, and you must be fully self-reliant, including for your own safety. For everyone else, it is an excellent month to build fitness, refine a gear list and lock in summer refuge bookings before the most popular dates go.
Tip · Use February for training: regular long days with plenty of climbing now will make your summer on the GR20 far more comfortable.
Month by month
The GR20 in March
Still winter up high
Spring reaches the Corsican coast, but at altitude March is still winter: snow continues to cover the high passes and the GR20 remains a mountaineering route requiring specialist gear and skills. The contrast is the real trap — it can feel mild in Calenzana or Conca while the ridgeline sits in full winter condition. The refuges are still unstaffed (no warden, no meals), the trail is essentially empty, and the days remain short. This is a month for lower-altitude Corsican trails — the Mare e Monti or coastal paths — while the high ridges of the GR20 stay the preserve of experienced alpinists.
Tip · Start following the Park's trail-condition updates in March: watching the snow melt month by month tells you more than any average ever will.
Month by month
The GR20 in April
Lingering snow, alpine terrain
April clears the valleys, not the ridges. A concrete marker: on 20 April 2026 the Park was still reporting snow on stages 3, 4, 7 and 9 (a status relayed by the FFRandonnée on 28 April). Passages above 2,000 m therefore remain mountaineering terrain, requiring an ice axe and crampons — and the ability to use them. The refuges are not yet staffed: the warden season only starts on 16 May, and the trail stays close to deserted. A full April traverse only makes sense for highly experienced mountaineers; for everyone else, it is the month of final adjustments — gear, training and bookings.
Tip · Before any early-season plan, read the Park's latest trail-condition update: it is the authority on actual snow cover.
Month by month
The GR20 in May
Snow: mountaineering terrain
May is a hinge month — and it still leans toward winter. Snow often holds on the high passes and mountaineering equipment (ice axe, crampons) can remain necessary: a May traverse should be prepared like an alpine outing, not a hike. The season does open, though: refuge wardens start on 16 May 2026, bringing back meals and bookings, even if not every service is immediately available. In exchange you get a true mountain atmosphere, genuine solitude and beautiful spring light. May is for hikers experienced on snow-covered terrain, after a serious check of actual conditions with the Park a few days before departure.
Tip · If you are aiming for late May, start after the 16th: staffed refuges, meals and bookings completely change the logistics.
Month by month
The GR20 in June
Good from mid-June (snowfields)
June truly opens the season: long days, staffed refuges, still-moderate heat and far fewer hikers than in midsummer. Some vigilance is still required: snowfields can linger on the high passes until mid-June, sometimes late June in heavy-snow years — the Park then recommends an ice axe and crampons, so check actual trail conditions before setting out. Afternoon thunderstorms, the GR20's number-one danger, already call for early-morning starts. And open fires are banned from 15 June (through 30 September): stoves only in the designated areas at refuges. From mid-June onwards, this is often one of the best windows of the entire year.
Tip · If you can choose, aim for the second half of the month: most snowfields have melted and the weather window is often excellent.
Month by month
The GR20 in July
Ideal window
Staffed refuges, supplies on site, simple logistics: July is one of the most favourable windows on the GR20, with weather that is often stable in the morning. Three things demand attention. Heat first, with water sources sometimes far apart: dehydration is summer's most underestimated risk. Then the afternoon thunderstorms — the number-one danger on the GR20, best defused by early starts. Finally the crowds: of roughly 15,000 hikers a year, the peaks concentrate in July and August, so refuges fill up and booking well ahead is essential. Reminder: open fires are banned across Corsica from 15 June to 30 September. A very good option, including for a well-prepared first traverse.
Tip · Start at dawn to clear the ridges before the afternoon storms, and ask the warden each morning whether the next spring is still running.
Month by month
The GR20 in August
Doable, hot and crowded
The month we hiked it ourselves — it worked, but it is not the easiest option. On the practical side: staffed refuges, predictable resupply, easier logistics for families. On the harsh side: it is the hottest, busiest month of the year, late-afternoon thunderstorms remain the number-one danger, and some springs that flow reliably in early summer run dry — water needs serious, stage-by-stage planning. Early starts stop being advice and become close to mandatory, both for the heat and for the storms. Doable for a prepared hiker who books far in advance and accepts pre-dawn alarms.
Tip · On stages known to be dry, leave with full water capacity and check with the warden each morning which springs are still flowing.
Month by month
The GR20 in September
Ideal window
Generally more bearable heat, a much quieter trail than midsummer, and superb light: September is, along with late June and early July, one of the most balanced windows on the GR20. Refuges stay staffed until 4 October 2026, so the logistics still hold. Two caveats. Days get shorter and the weather can turn: this is when Mediterranean episodes begin — bursts of sometimes violent rain, possible from September to November — so watch the forecasts closely. And September is no longer a secret: bookings show real peaks outside July-August, so reserve early anyway. For anyone wanting calm without giving up services, it is often the best choice.
Tip · Book your refuges as soon as your dates are set: outside July-August, September is where the real booking peaks happen.
Month by month
The GR20 in October
End of season
Quiet trails, autumn colours, a mountain returned to itself: October has real charm, but it is end-of-season in the strict sense. Refuge staffing ends on 4 October 2026: beyond that date they stay open but with no warden, no meals and no booking — full self-sufficiency is mandatory. Add reduced or closed services along the route, settling cold, noticeably shorter days and less stable weather, with Mediterranean episodes still possible into November. This month is for experienced, self-sufficient hikers, ideally within the very first days. For a first traverse, it is a no.
Tip · If you attempt October, plan your traverse for the first days of the month so you finish before staffing ends on the 4th.
Month by month
The GR20 in November
Off-season, not advised
November is when the Corsican mountains tip into winter, on a deserted trail. Refuges have been unstaffed since 4 October: they stay open as bare shelters, with no warden, no meals, no booking. It is also the heart of the Mediterranean-episode season: bursts of sometimes torrential rain that can make streams and passages impassable. Higher up, the first winter conditions can set in, and very short days leave little margin for error. Almost nobody is on the route: if something goes wrong, no other hiker will pass by. A full traverse is not advised; only short outings, by highly self-sufficient mountaineers within a confirmed weather window, are worth discussing.
Tip · Lock nothing in ahead of time: watch for Mediterranean-episode alerts and be ready to cancel without regret.
Month by month
The GR20 in December
Winter mountaineering only
In December the GR20 changes nature: in winter conditions it is no longer hiking but a mountaineering route, with everything that implies in equipment, technique and snow experience. Refuges are unstaffed — open as bare shelters, with no warden, no meals, no booking — and the summer waymarking was never designed for winter. A note of honesty: no official Meteo-France climate normals exist above roughly 1,000-1,500 m in Corsica, so no precise altitude temperature figure can seriously be published. Think in conditions, not degrees. Strictly for seasoned mountaineers, ideally led by a professional guide.
Tip · If winter genuinely tempts you, go with a qualified mountain guide — never on an improvised solo attempt.
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