Danube Cycle Path - part Romania - leg 4.2b: which way and when to ride
The best month for Danube Cycle Path - part Romania - leg 4.2b is September: 84% of days were dry with highs of 10–30 °C. In September, riding Tulcea → Constanţa meant an average tailwind of 3.5 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 | 13% | 12% | 42 | 4 °C | 0% | 86% | 9.2 † |
| February | 21% | 11% | 28 | 6 °C | 0% | 77% | 10.4 † |
| March | 49% | 16% | 35 | 11 °C | 0% | 46% | 11.8 |
| April | 78% | 18% | 40 | 16 °C | 0% | 7% | 13.4 |
| May | 77% | 23% | 51 | 21 °C | 1% | 0% | 14.8 |
| June | 63% | 23% | 54 | 27 °C | 16% | 0% | 15.6 |
| July | 45% | 19% | 40 | 29 °C | 41% | 0% | 15.2 |
| August | 48% | 9% | 27 | 30 °C | 45% | 0% | 14.0 |
| September | 84% | 11% | 37 | 24 °C | 5% | 0% | 12.4 |
| October | 84% | 12% | 46 | 17 °C | 0% | 5% | 10.9 † |
| November | 55% | 12% | 41 | 11 °C | 0% | 37% | 9.5 † |
| December | 18% | 13% | 44 | 6 °C | 0% | 79% | 8.8 † |
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 Constanţa → Tulcea, km/h | Headwind > 15 km/h, Constanţa → Tulcea | Headwind > 15 km/h, Tulcea → Constanţa | Better way |
|---|---|---|---|---|
| January | −2.2 | 18% | 7% | Tulcea → Constanţa |
| February | −2.3 | 18% | 8% | Tulcea → Constanţa |
| March | −1.9 | 18% | 10% | either |
| April | −0.4 | 13% | 8% | either |
| May | −0.2 | 10% | 8% | either |
| June | −1.9 | 11% | 5% | either |
| July | −2.7 | 11% | 4% | Tulcea → Constanţa |
| August | −4.2 | 15% | 3% | Tulcea → Constanţa |
| September | −3.5 | 15% | 5% | Tulcea → Constanţa |
| October | −2.6 | 15% | 6% | Tulcea → Constanţa |
| November | −0.5 | 11% | 9% | either |
| December | −2.1 | 15% | 6% | Tulcea → Constanţa |
Along the route (sections of about 25 km)
| km | Heading | Tailwind in September, km/h |
|---|---|---|
| 0–26 | N | −4.0 |
| 26–51 | N | −3.5 |
| 51–77 | N | −3.0 |
| 77–105 | NE | −4.2 |
| 105–130 | N | −3.6 |
| 130–149 | N | −2.7 |
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.