Route des Grandes Alpes à vélo - Tracé principal, stage 1: Thonon-les-Bains → Beaufort
On stage 1 (Thonon-les-Bains → Beaufort, 128 km) the best month is September: 66% of days were dry with highs of 10–30 °C; the wind barely favours either direction (1.6 km/h on average; ERA5 2006–2025, 9:00–18:00).
← Route des Grandes Alpes à vélo - Tracé principal (Whole route)
Weather by month
| Month | Good days | Rain days ≥ 1 mm | Rain, mm | Avg high | Days ≥ 30 °C | Days < 10 °C | Daylight, h |
|---|---|---|---|---|---|---|---|
| January | 2% | 30% | 140 | 2 °C | 0% | 98% | 9.0 † |
| February | 9% | 28% | 103 | 4 °C | 0% | 91% | 10.3 † |
| March | 26% | 34% | 129 | 7 °C | 0% | 71% | 11.8 |
| April | 44% | 41% | 116 | 12 °C | 0% | 36% | 13.5 |
| May | 42% | 56% | 190 | 15 °C | 0% | 17% | 14.9 |
| June | 50% | 50% | 155 | 19 °C | 1% | 1% | 15.7 |
| July | 57% | 42% | 154 | 21 °C | 1% | 0% | 15.4 |
| August | 62% | 36% | 138 | 21 °C | 1% | 1% | 14.1 |
| September | 66% | 33% | 115 | 17 °C | 0% | 6% | 12.5 |
| October | 63% | 25% | 108 | 13 °C | 0% | 23% | 10.8 † |
| November | 22% | 31% | 136 | 7 °C | 0% | 76% | 9.4 † |
| December | 1% | 32% | 165 | 2 °C | 0% | 99% | 8.7 † |
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 → Beaufort, km/h | Headwind > 15 km/h, Thonon-les-Bains → Beaufort | Headwind > 15 km/h, Beaufort → Thonon-les-Bains | Better way |
|---|---|---|---|---|
| January | −1.2 | 0% | 0% | either |
| February | −0.3 | 0% | 0% | either |
| March | +0.7 | 0% | 0% | either |
| April | +1.7 | 0% | 0% | either |
| May | +1.8 | 0% | 0% | either |
| June | +1.9 | 0% | 0% | either |
| July | +1.8 | 0% | 0% | either |
| August | +1.7 | 0% | 0% | either |
| September | +1.6 | 0% | 0% | either |
| October | +0.4 | 0% | 0% | either |
| November | −0.7 | 0% | 0% | either |
| December | −1.7 | 0% | 0% | either |
Along the route (sections of about 25 km)
| km | Heading | Tailwind in September, km/h |
|---|---|---|
| 0–25 | SE | +2.2 |
| 25–50 | SW | +1.9 |
| 50–75 | SW | −0.1 |
| 75–101 | S | +1.8 |
| 101–128 | SE | +2.2 |
Other stages
- Thonon-les-Bains → Beaufort 128 km
- Beaufort → Modane 151 km
- Modane → Guillestre 134 km
- Guillestre → Péone 116 km
- Péone → Nice 168 km
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.