Route des Grandes Alpes à vélo - Tracé principal: which way and when to ride
The best month for Route des Grandes Alpes à vélo - Tracé principal is August: 65% of days were dry with highs of 10–30 °C. In August the wind barely favours either direction — on average 0.0 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 | 6% | 23% | 100 | 0 °C | 0% | 94% | 9.1 † |
| February | 10% | 23% | 79 | 2 °C | 0% | 89% | 10.3 † |
| March | 19% | 28% | 107 | 5 °C | 0% | 79% | 11.8 |
| April | 28% | 36% | 103 | 8 °C | 0% | 60% | 13.4 |
| May | 35% | 50% | 140 | 12 °C | 0% | 36% | 14.8 |
| June | 48% | 51% | 121 | 17 °C | 0% | 7% | 15.6 |
| July | 60% | 39% | 95 | 20 °C | 0% | 1% | 15.3 |
| August | 65% | 34% | 88 | 20 °C | 1% | 2% | 14.1 |
| September | 63% | 33% | 87 | 16 °C | 0% | 11% | 12.4 |
| October | 54% | 25% | 103 | 12 °C | 0% | 35% | 10.9 † |
| November | 20% | 27% | 131 | 5 °C | 0% | 77% | 9.5 † |
| December | 7% | 24% | 123 | 1 °C | 0% | 92% | 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 Thonon-les-Bains → Nice, km/h | Headwind > 15 km/h, Thonon-les-Bains → Nice | Headwind > 15 km/h, Nice → Thonon-les-Bains | Better way |
|---|---|---|---|---|
| January | +0.5 | 0% | 0% | either |
| February | +0.4 | 0% | 0% | either |
| March | +0.4 | 0% | 0% | either |
| April | +0.1 | 0% | 0% | either |
| May | +0.1 | 0% | 0% | either |
| June | −0.1 | 0% | 0% | either |
| July | +0.1 | 0% | 0% | either |
| August | 0.0 | 0% | 0% | either |
| September | −0.1 | 0% | 0% | either |
| October | −0.2 | 0% | 0% | either |
| November | +0.2 | 0% | 0% | either |
| December | +0.4 | 0% | 0% | either |
Stages
The route is split into 5 stages of about 100–150 km between towns; each stage has its own page.
| Stage | km | Best month | Tailwind Thonon-les-Bains → Nice in August, km/h |
|---|---|---|---|
| 1. Thonon-les-Bains → Beaufort | 128 | September | +1.7 |
| 2. Beaufort → Modane | 151 | August | +1.1 |
| 3. Modane → Guillestre | 134 | August | 0.0 |
| 4. Guillestre → Péone | 116 | August | −1.0 |
| 5. Péone → Nice | 168 | October | −1.7 |
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.