National Cycle Network Route 4, stage 5: Carmarthen → Fishguard
On stage 5 (Carmarthen → Fishguard, 147 km) the best month is June: 74% of days were dry with highs of 10–30 °C, and riding Fishguard → Carmarthen meant an average tailwind of 3.0 km/h (ERA5 2006–2025, 9:00–18:00).
← National Cycle Network Route 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 | 16% | 30% | 108 | 8 °C | 0% | 68% | 8.3 † |
| February | 15% | 27% | 82 | 8 °C | 0% | 74% | 9.9 † |
| March | 28% | 27% | 78 | 9 °C | 0% | 61% | 11.7 |
| April | 62% | 22% | 59 | 11 °C | 0% | 24% | 13.8 |
| May | 74% | 25% | 70 | 14 °C | 0% | 2% | 15.6 |
| June | 74% | 26% | 73 | 16 °C | 0% | 0% | 16.7 |
| July | 71% | 29% | 82 | 18 °C | 0% | 0% | 16.2 |
| August | 71% | 29% | 90 | 18 °C | 0% | 0% | 14.6 |
| September | 72% | 28% | 93 | 17 °C | 0% | 0% | 12.6 |
| October | 68% | 30% | 120 | 14 °C | 0% | 2% | 10.5 † |
| November | 42% | 38% | 124 | 11 °C | 0% | 26% | 8.7 † |
| December | 24% | 37% | 132 | 9 °C | 0% | 50% | 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 Carmarthen → Fishguard, km/h | Headwind > 15 km/h, Carmarthen → Fishguard | Headwind > 15 km/h, Fishguard → Carmarthen | Better way |
|---|---|---|---|---|
| January | −2.8 | 27% | 18% | Fishguard → Carmarthen |
| February | −1.7 | 26% | 21% | either |
| March | −1.0 | 23% | 19% | either |
| April | −0.7 | 18% | 16% | either |
| May | −2.5 | 20% | 13% | Fishguard → Carmarthen |
| June | −3.0 | 20% | 11% | Fishguard → Carmarthen |
| July | −4.0 | 23% | 11% | Fishguard → Carmarthen |
| August | −4.0 | 26% | 12% | Fishguard → Carmarthen |
| September | −2.5 | 23% | 15% | Fishguard → Carmarthen |
| October | −0.9 | 24% | 20% | either |
| November | −2.8 | 28% | 19% | Fishguard → Carmarthen |
| December | −2.9 | 29% | 19% | Fishguard → Carmarthen |
Along the route (sections of about 25 km)
| km | Heading | Tailwind in June, km/h |
|---|---|---|
| 498–523 | SW | −7.3 |
| 523–548 | SW | −7.4 |
| 548–574 | NW | −5.1 |
| 574–600 | NW | −2.5 |
| 600–625 | N | −0.3 |
| 625–645 | NE | +6.4 |
Other stages
- London → Reading 116 km
- Reading → Bath 128 km
- Bath → Pontypridd 129 km
- Pontypridd → Carmarthen 126 km
- Carmarthen → Fishguard 147 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.