National Cycle Network Route 4: which way and when to ride
The best month for National Cycle Network Route 4 is September: 75% of days were dry with highs of 10–30 °C. In September, riding Fishguard → London meant an average tailwind of 3.7 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 | 14% | 26% | 87 | 8 °C | 0% | 75% | 8.3 † |
| February | 19% | 25% | 71 | 8 °C | 0% | 73% | 9.9 † |
| March | 38% | 26% | 67 | 10 °C | 0% | 51% | 11.7 |
| April | 66% | 24% | 53 | 13 °C | 0% | 17% | 13.8 |
| May | 71% | 28% | 71 | 15 °C | 0% | 2% | 15.6 |
| June | 74% | 25% | 69 | 18 °C | 0% | 0% | 16.6 |
| July | 72% | 27% | 76 | 20 °C | 1% | 0% | 16.2 |
| August | 71% | 28% | 80 | 19 °C | 1% | 0% | 14.6 |
| September | 75% | 25% | 74 | 18 °C | 0% | 0% | 12.6 |
| October | 71% | 27% | 97 | 14 °C | 0% | 3% | 10.5 † |
| November | 43% | 30% | 99 | 11 °C | 0% | 34% | 8.8 † |
| December | 23% | 29% | 101 | 9 °C | 0% | 59% | 7.8 † |
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 London → Fishguard, km/h | Headwind > 15 km/h, London → Fishguard | Headwind > 15 km/h, Fishguard → London | Better way |
|---|---|---|---|---|
| January | −4.8 | 25% | 10% | Fishguard → London |
| February | −3.5 | 25% | 13% | Fishguard → London |
| March | −2.0 | 21% | 14% | Fishguard → London |
| April | −0.6 | 16% | 13% | either |
| May | −2.7 | 20% | 10% | Fishguard → London |
| June | −3.6 | 19% | 7% | Fishguard → London |
| July | −6.1 | 24% | 5% | Fishguard → London |
| August | −6.0 | 26% | 6% | Fishguard → London |
| September | −3.7 | 21% | 9% | Fishguard → London |
| October | −2.6 | 20% | 12% | Fishguard → London |
| November | −4.0 | 23% | 10% | Fishguard → London |
| December | −4.9 | 26% | 10% | Fishguard → London |
Stages
The route is split into 5 stages of about 100–150 km between towns; each stage has its own page.
| Stage | km | Best month | Tailwind London → Fishguard in September, km/h |
|---|---|---|---|
| 1. London → Reading | 116 | September | −3.9 |
| 2. Reading → Bath | 128 | September | −5.0 |
| 3. Bath → Pontypridd | 129 | September | −3.7 |
| 4. Pontypridd → Carmarthen | 126 | September | −3.5 |
| 5. Carmarthen → Fishguard | 147 | June | −2.5 |
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.