NAP-route: which way and when to ride
The best month for NAP-route is September: 75% of days were dry with highs of 10–30 °C. In September, riding Utrecht → Bunde meant an average tailwind of 4.4 km/h (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% | 27% | 69 | 5 °C | 0% | 89% | 8.1 † |
| February | 13% | 26% | 59 | 6 °C | 0% | 82% | 9.8 † |
| March | 37% | 24% | 54 | 10 °C | 0% | 55% | 11.7 |
| April | 61% | 24% | 48 | 14 °C | 0% | 22% | 13.9 |
| May | 70% | 28% | 67 | 17 °C | 0% | 3% | 15.8 |
| June | 71% | 27% | 73 | 20 °C | 2% | 0% | 16.8 |
| July | 60% | 35% | 92 | 22 °C | 6% | 0% | 16.4 |
| August | 63% | 33% | 86 | 22 °C | 4% | 0% | 14.7 |
| September | 75% | 24% | 63 | 19 °C | 0% | 0% | 12.6 |
| October | 70% | 25% | 73 | 14 °C | 0% | 7% | 10.5 † |
| November | 32% | 25% | 62 | 9 °C | 0% | 55% | 8.6 † |
| December | 10% | 25% | 68 | 7 °C | 0% | 83% | 7.6 † |
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 Bunde → Utrecht, km/h | Headwind > 15 km/h, Bunde → Utrecht | Headwind > 15 km/h, Utrecht → Bunde | Better way |
|---|---|---|---|---|
| January | −7.4 | 30% | 4% | Utrecht → Bunde |
| February | −5.5 | 26% | 8% | Utrecht → Bunde |
| March | −3.1 | 21% | 9% | Utrecht → Bunde |
| April | −0.8 | 15% | 10% | either |
| May | −1.0 | 16% | 9% | either |
| June | −2.7 | 16% | 5% | Utrecht → Bunde |
| July | −5.2 | 20% | 3% | Utrecht → Bunde |
| August | −5.4 | 20% | 3% | Utrecht → Bunde |
| September | −4.4 | 20% | 4% | Utrecht → Bunde |
| October | −5.8 | 25% | 4% | Utrecht → Bunde |
| November | −6.5 | 26% | 4% | Utrecht → Bunde |
| December | −8.3 | 32% | 4% | Utrecht → Bunde |
Along the route (sections of about 25 km)
| km | Heading | Tailwind in September, km/h |
|---|---|---|
| 0–25 | SW | −5.3 |
| 25–51 | NW | −3.0 |
| 51–76 | W | −4.1 |
| 76–101 | SW | −5.5 |
| 101–127 | S | −4.3 |
| 127–153 | SW | −4.7 |
| 153–178 | SW | −4.4 |
| 178–204 | S | −4.0 |
| 204–229 | S | −3.2 |
| 229–255 | W | −4.6 |
| 255–282 | SW | −5.0 |
| 282–307 | SW | −4.6 |
| 307–333 | SW | −4.8 |
| 333–349 | SW | −4.7 |
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.