7: Nacionālais upju maršruts: which way and when to ride
The best month for 7: Nacionālais upju maršruts is September: 74% of days were dry with highs of 10–30 °C. In September the wind barely favours either direction — on average 0.6 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% | 23% | 54 | -2 °C | 0% | 100% | 7.4 † |
| February | 0% | 21% | 40 | -1 °C | 0% | 100% | 9.4 † |
| March | 12% | 21% | 41 | 4 °C | 0% | 88% | 11.6 |
| April | 49% | 23% | 45 | 11 °C | 0% | 45% | 14.2 |
| May | 69% | 26% | 60 | 17 °C | 0% | 9% | 16.4 |
| June | 70% | 28% | 74 | 21 °C | 2% | 0% | 17.8 |
| July | 62% | 35% | 92 | 23 °C | 4% | 0% | 17.2 |
| August | 66% | 31% | 91 | 22 °C | 3% | 0% | 15.2 |
| September | 74% | 24% | 57 | 17 °C | 0% | 3% | 12.7 |
| October | 40% | 26% | 68 | 10 °C | 0% | 47% | 10.2 † |
| November | 5% | 21% | 56 | 5 °C | 0% | 94% | 8.0 † |
| December | 0% | 23% | 52 | 1 °C | 0% | 100% | 6.8 † |
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 Salacgrīva → near Daugavpils, km/h | Headwind > 15 km/h, Salacgrīva → near Daugavpils | Headwind > 15 km/h, near Daugavpils → Salacgrīva | Better way |
|---|---|---|---|---|
| January | −2.3 | 13% | 7% | near Daugavpils → Salacgrīva |
| February | −1.8 | 10% | 7% | either |
| March | +0.3 | 8% | 10% | either |
| April | +1.7 | 6% | 11% | either |
| May | +1.5 | 5% | 8% | either |
| June | +2.0 | 4% | 9% | Salacgrīva → near Daugavpils |
| July | +1.4 | 4% | 7% | either |
| August | −0.2 | 6% | 5% | either |
| September | −0.6 | 8% | 7% | either |
| October | −1.6 | 12% | 7% | either |
| November | −3.2 | 12% | 5% | near Daugavpils → Salacgrīva |
| December | −2.9 | 14% | 6% | near Daugavpils → Salacgrīva |
Along the route (sections of about 25 km)
| km | Heading | Tailwind in September, km/h |
|---|---|---|
| 0–25 | E | +3.1 |
| 25–52 | S | −2.7 |
| 52–77 | S | −3.3 |
| 77–103 | SE | −0.3 |
| 103–128 | SW | −4.0 |
| 128–154 | SW | −3.9 |
| 154–179 | SE | +1.0 |
| 179–204 | SE | −1.4 |
| 204–229 | E | +1.3 |
| 229–255 | E | +2.3 |
| 255–280 | SE | +1.0 |
| 280–305 | SE | −0.1 |
| 305–331 | SE | −0.8 |
| 331–357 | S | −2.3 |
| 357–372 | E | +2.3 |
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.