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A scorching summer 2025 on Corsica — heat lessons for GR20 hikers
Summer 2025 was a hot one on Corsica. According to Santé publique France, the island went through two heatwave episodes, the first striking early and lasting long — roughly 19 June to 6 July, some 18 days. For anyone on the GR20 that window, the heat was not a background detail: it shaped every climb.
Why heat bites harder on the GR20
The GR20 is famously shadeless. Long stretches cross bare granite, scree and exposed ridgeline where there is no vegetation and nowhere to hide from the sun. On that terrain the temperature felt underfoot climbs well above the official readings, dehydration accelerates, your heart rate rises, and the big daily climbs that are hard in cool weather become genuinely risky.
How to walk it safely in a heatwave
- Start at first light. Get the day's biggest climb done before the sun is high; aim to be off the most exposed sections by early afternoon.
- Carry more water than you think, and know where the next reliable spring or refuge is before you leave one.
- Respect fire bans. Corsica restricts access and open flame during high fire-risk spells — check local rules.
- Be ready to wait. A rest day at Vizzavona or Haut-Asco beats a heatstroke on a ridge.
Let the plan do the work
Timing your hardest stages for the cool of the morning is a planning problem. Our free planner splits the GR20 into realistic days for your fitness and pairs each morning with a weather briefing, so you can dodge the worst heat on the most exposed stretches. See also our guide on <a href="/guide/when-to-go/">when to go</a>.
Plan your own GR20
Set your pace, see live refuge availability, offline maps and a daily weather briefing — free.
Open the GR20 planner