GreenlyFrost dates and when to plant in Wales
United Kingdom
In Wales the last spring frost comes between 28 February (Swansea) and 7 April (Wrexham) — the median of 2016–2025 in 3 cities. The first autumn frost comes between 22 November (Cardiff) and 1 December (Swansea). The frost-free season lasts 230–276 days. Tomato: plant out into open ground 24 May – 11 August, earliest in Swansea, latest in Swansea.
Frost dates by city in Wales
| City | Last spring frost | First autumn frost | Frost-free days | Climate zone | Tomato: window |
|---|---|---|---|---|---|
| Swansea | 28 February | 1 December | 276 | 270 frost-free days or more | 24 May – 11 August |
| Cardiff | 25 March | 22 November | 242 | 210–269 frost-free days | 26 May – 2 August |
| Wrexham | 7 April | 23 November | 230 | 210–269 frost-free days | 5 June – 3 August |
Median of 2016–2025 for the 25 km grid cell of the city: the last day at or below 0 °C in spring and the first in autumn (ERA5 reanalysis via Open-Meteo). In a cold year a frost can come a week or two later — Greenly warns 48 hours ahead.
When to plant in Wales: windows by crop
The earliest start and the latest end among the cities here, each with its city; every city’s own window is on its page. Each window starts on the Greenly calendar date and ends on the last day that still leaves the crop’s days to harvest (from its card) before the average first autumn frost, plus six weeks of picking for crops harvested over weeks (tomatoes, peppers, aubergines, cucumbers, courgettes, pumpkins, watermelons, beans) — our rule; earlier in the window is safer.
| Crop | Planting out or sowing |
|---|---|
| Tomato | 24 May (Swansea) – 11 August (Swansea) |
| Cucumber | 21 June (Swansea) – 16 September (Swansea) |
| Bell Pepper, Eggplant | 21 June (Swansea) – 11 August (Swansea) |
| Zucchini | 21 June (Swansea) – 14 September (Swansea) |
| Pumpkin | 21 June (Swansea) – 6 August (Swansea) |
| Watermelon | 21 June (Swansea) – 22 August (Swansea) |
| Peas | 7 February (Swansea) – 18 September (Swansea) |
| Garlic, Tulip, Daffodil, Crocus, Hyacinth | Autumn planting: 23 October (Cardiff) – end of December (Cardiff) |
Weather by month in Wales
Across the 3 cities the warmest month is July (average days 19.7 … 20.7 °C) and the coldest January (average nights 2.3 … 3.7 °C). No city here averages below 0 °C at night in any month.
| Month | Day, °C | Night, °C | Rain, mm |
|---|---|---|---|
| January | 7.2 … 8.2 °C | 2.3 … 3.7 °C | 106 |
| February | 8.3 … 8.9 °C | 2.8 … 4.4 °C | 110 |
| March | 9.9 … 10.4 °C | 3.3 … 4.7 °C | 106 |
| April | 12.4 … 13.1 °C | 4.4 … 6.1 °C | 76 |
| May | 16 … 16.6 °C | 8 … 9.4 °C | 80 |
| June | 18.3 … 19.2 °C | 11.1 … 12.4 °C | 83 |
| July | 19.7 … 20.7 °C | 12.6 … 13.9 °C | 85 |
| August | 19.4 … 20.3 °C | 12.6 … 14.1 °C | 91 |
| September | 17.4 … 18 °C | 10.8 … 12.5 °C | 114 |
| October | 13.8 … 14.7 °C | 8.2 … 10.2 °C | 141 |
| November | 9.7 … 11.2 °C | 5 … 6.8 °C | 119 |
| December | 8.2 … 9.4 °C | 3.8 … 5.6 °C | 149 |
Day and night: the lowest … highest monthly average among the cities; rain: the middle city (ERA5 via Open-Meteo).
What to plant month by month: the UK
Other regions: United Kingdom
More about the United Kingdom
- Gardening in the United Kingdom: climate zones and crops by region
- United Kingdom: frost dates by city
- When to plant tomatoes in the United Kingdom
- When to plant cucumbers in the United Kingdom
- When to plant bell peppers in the United Kingdom
- When to plant peas in the United Kingdom
- When to plant garlic in the United Kingdom
- Gardening by country
