Every Font boulderer has their climbing window they swear by for booking trips, but what does the data say?
We ran our Font-specific climbingforecast.co.uk model with 30 years of Météo-France norms to find out when you should book the trip for peak conditions.
The Sweet Spot: September. It has a 70% chance of being climbable, has less rain than spring and avoids the heat in July and August. Climb in the early mornings for the best friction and then enjoy the afternoon sun!
When to avoid: November to February. It's generally a grim forecast with short days, persistent humidity and the forest stays damp.
Once you make it there, remember to check climbingforecast.co.uk before you decide which area to go to!
| Month | Green Days | Amber Days | Red Days | % Green | Green + Amber |
|---|---|---|---|---|---|
| Jan | 6.0 | 9.6 | 15.5 | 19% | 50% |
| Feb | 5.5 | 10.0 | 12.5 | 20% | 55% |
| Mar | 6.3 | 12.3 | 12.4 | 20% | 60% |
| Apr | 8.0 | 12.1 | 9.9 | 27% | 67% |
| May | 7.2 | 12.5 | 11.3 | 23% | 64% |
| Jun | 6.9 | 13.5 | 9.6 | 23% | 68% |
| Jul | 7.8 | 14.3 | 8.8 | 25% | 71% |
| Aug | 8.5 | 13.6 | 8.9 | 27% | 71% |
| Sep ★ | 8.8 | 12.3 | 9.0 | 29% | 70% |
| Oct | 5.5 | 11.9 | 13.5 | 18% | 56% |
| Nov | 4.9 | 10.7 | 14.4 | 16% | 52% |
| Dec | 4.0 | 9.2 | 17.8 | 13% | 43% |
Based on 30 simulated years using Météo-France 1991–2020 climate norms, averaged across 12 Fontainebleau sectors. Factors in rain, wind, humidity, and a sandstone friction penalty for hot/humid days.
Peak Potential
September is your best bet — 29% green days, 70% climbable overall, and friction holds up because the worst of the summer heat has passed.
Winter Slump
December and November are the toughest, with red days at 17.8 and 14.4 respectively. Persistent humidity and dense forest mean the rock stays damp for days.
The Sweet Spot
April to September offers the most consistency — the "Green + Amber" percentage never drops below 64% across this window.
Good luck and enjoy the climbing!