Nasjonal sykkelrute 4: which way and when to ride
The best month for Nasjonal sykkelrute 4 is June: 56% of days were dry with highs of 10–30 °C. In June the wind barely favours either direction — on average 0.2 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 | 0% | 30% | 95 | -4 °C | 0% | 100% | 6.5 † |
| February | 0% | 24% | 69 | -3 °C | 0% | 100% | 9.0 † |
| March | 2% | 25% | 73 | 0 °C | 0% | 98% | 11.6 |
| April | 14% | 24% | 58 | 5 °C | 0% | 85% | 14.5 |
| May | 37% | 32% | 80 | 10 °C | 0% | 54% | 17.2 |
| June | 56% | 37% | 104 | 15 °C | 0% | 18% | 19.0 |
| July | 53% | 45% | 131 | 17 °C | 0% | 7% | 18.3 |
| August | 54% | 43% | 126 | 15 °C | 0% | 9% | 15.7 |
| September | 45% | 34% | 115 | 11 °C | 0% | 40% | 12.8 |
| October | 10% | 32% | 111 | 5 °C | 0% | 87% | 9.9 † |
| November | 1% | 29% | 98 | 0 °C | 0% | 99% | 7.2 † |
| December | 0% | 31% | 102 | -3 °C | 0% | 100% | 5.7 † |
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 Asker → Ål, km/h | Headwind > 15 km/h, Asker → Ål | Headwind > 15 km/h, Ål → Asker | Better way |
|---|---|---|---|---|
| January | −0.9 | 3% | 1% | either |
| February | −0.5 | 2% | 1% | either |
| March | −0.4 | 3% | 1% | either |
| April | −0.4 | 3% | 2% | either |
| May | 0.0 | 2% | 1% | either |
| June | +0.2 | 3% | 2% | either |
| July | +0.4 | 2% | 1% | either |
| August | +0.4 | 2% | 1% | either |
| September | +0.1 | 3% | 2% | either |
| October | 0.0 | 2% | 1% | either |
| November | −0.4 | 2% | 1% | either |
| December | −1.0 | 2% | 1% | either |
Stages
The route is split into 4 stages of about 100–150 km between towns; each stage has its own page.
| Stage | km | Best month | Tailwind Asker → Ål in June, km/h |
|---|---|---|---|
| 1. Asker → Flå | 135 | September | +1.3 |
| 2. Flå → Geilo | 115 | June | −1.6 |
| 3. Geilo → near Lærdalsøyri | 136 | August | −1.0 |
| 4. near Lærdalsøyri → Ål | 155 | June | +1.6 |
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.