La Grande Traversée du Volcan à Vélo - GT2V: which way and when to ride
The best month for La Grande Traversée du Volcan à Vélo - GT2V is September: 74% of days were dry with highs of 10–30 °C. In September the wind barely favours either direction — on average 1.4 km/h along the route (ERA5 2006–2025, daytime 9:00–18:00).
Weather by month
| Month | Good days | Rain days ≥ 1 mm | Rain, mm | Avg high | Days ≥ 30 °C | Days < 10 °C | Daylight, h |
|---|---|---|---|---|---|---|---|
| January | 11% | 30% | 101 | 5 °C | 0% | 87% | 9.1 † |
| February | 27% | 27% | 78 | 7 °C | 0% | 69% | 10.3 † |
| March | 42% | 32% | 100 | 10 °C | 0% | 48% | 11.8 |
| April | 57% | 35% | 94 | 14 °C | 0% | 22% | 13.4 |
| May | 59% | 40% | 111 | 17 °C | 0% | 7% | 14.8 |
| June | 62% | 34% | 101 | 21 °C | 4% | 0% | 15.6 |
| July | 66% | 26% | 77 | 24 °C | 10% | 0% | 15.3 |
| August | 66% | 23% | 78 | 24 °C | 11% | 0% | 14.1 |
| September | 74% | 24% | 81 | 20 °C | 1% | 2% | 12.4 |
| October | 70% | 23% | 92 | 16 °C | 0% | 11% | 10.9 † |
| November | 36% | 32% | 111 | 10 °C | 0% | 51% | 9.5 † |
| December | 16% | 29% | 108 | 7 °C | 0% | 80% | 8.8 † |
Best months are all months within 3 percentage points of the best one. † less than 11 hours of daylight — long stages get tight.
Wind by month
| Month | Wind Brassac-les-Mines → Flagnac, km/h | Headwind > 15 km/h, Brassac-les-Mines → Flagnac | Headwind > 15 km/h, Flagnac → Brassac-les-Mines | Better way |
|---|---|---|---|---|
| January | −1.7 | 8% | 3% | either |
| February | −1.9 | 9% | 5% | either |
| March | −1.7 | 10% | 6% | either |
| April | −0.9 | 6% | 4% | either |
| May | −1.1 | 5% | 5% | either |
| June | −1.3 | 4% | 3% | either |
| July | −1.7 | 3% | 1% | either |
| August | −1.8 | 3% | 1% | either |
| September | −1.4 | 4% | 3% | either |
| October | −2.1 | 6% | 2% | Flagnac → Brassac-les-Mines |
| November | −2.4 | 8% | 3% | Flagnac → Brassac-les-Mines |
| December | −2.3 | 8% | 2% | Flagnac → Brassac-les-Mines |
Along the route (sections of about 25 km)
| km | Heading | Tailwind in September, km/h |
|---|---|---|
| 0–25 | SW | −0.3 |
| 25–51 | W | −2.1 |
| 51–76 | SW | −2.2 |
| 76–101 | SW | −1.9 |
| 101–127 | SW | −1.8 |
| 127–152 | SW | −1.6 |
| 152–177 | S | −0.9 |
| 177–183 | SE | +1.8 |
How to read the numbers
Wind is the 10 m wind of a 25-km grid cell, daytime hours 9:00–18:00 local solar time; at saddle height in a sheltered valley it is weaker, on a coast or ridge stronger. A positive value is a tailwind. ERA5 slightly over-counts days with ≥ 1 mm of rain (by about 5–7 percentage points) and underestimates daily highs by 1–2 °C. Good day = less than 1 mm of rain between 9:00 and 18:00 (riding hours, local solar time) and a high between 10 and 30 °C; rain at night or in the evening does not spoil it.