Nasjonal sykkelrute 4, stage 1: Asker → Flå
On stage 1 (Asker → Flå, 135 km) the best month is September: 71% of days were dry with highs of 10–30 °C; the wind barely favours either direction (1.0 km/h on average; ERA5 2006–2025, 9:00–18:00).
← Nasjonal sykkelrute 4 (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 | 0% | 24% | 82 | -3 °C | 0% | 100% | 6.7 † |
| February | 0% | 20% | 59 | -1 °C | 0% | 100% | 9.0 † |
| March | 8% | 18% | 58 | 4 °C | 0% | 92% | 11.6 |
| April | 37% | 18% | 50 | 9 °C | 0% | 61% | 14.5 |
| May | 63% | 28% | 82 | 14 °C | 0% | 17% | 17.1 |
| June | 70% | 30% | 98 | 19 °C | 0% | 0% | 18.8 |
| July | 63% | 36% | 129 | 20 °C | 1% | 0% | 18.1 |
| August | 65% | 35% | 123 | 19 °C | 0% | 0% | 15.6 |
| September | 71% | 26% | 107 | 15 °C | 0% | 6% | 12.7 |
| October | 30% | 26% | 101 | 9 °C | 0% | 62% | 10.0 † |
| November | 3% | 25% | 89 | 3 °C | 0% | 95% | 7.4 † |
| December | 0% | 25% | 76 | -2 °C | 0% | 100% | 5.9 † |
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 → Flå, km/h | Headwind > 15 km/h, Asker → Flå | Headwind > 15 km/h, Flå → Asker | Better way |
|---|---|---|---|---|
| January | −1.6 | 1% | 1% | either |
| February | −0.4 | 0% | 1% | either |
| March | −0.1 | 1% | 1% | either |
| April | −0.3 | 2% | 0% | either |
| May | +0.8 | 1% | 1% | either |
| June | +1.3 | 1% | 1% | either |
| July | +1.7 | 0% | 0% | either |
| August | +1.8 | 0% | 1% | either |
| September | +1.0 | 1% | 1% | either |
| October | +0.3 | 1% | 1% | either |
| November | −0.8 | 1% | 0% | either |
| December | −1.7 | 1% | 1% | either |
Along the route (sections of about 25 km)
| km | Heading | Tailwind in September, km/h |
|---|---|---|
| 0–25 | SW | −1.2 |
| 25–50 | NW | +0.9 |
| 50–75 | N | +2.0 |
| 75–100 | NW | +1.4 |
| 100–126 | N | +2.1 |
| 126–135 | NW | +0.2 |
Other stages
- Asker → Flå 135 km
- Flå → Geilo 115 km
- Geilo → near Lærdalsøyri 136 km
- near Lærdalsøyri → Ål 155 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.