GreenlyGardening in Ireland: climate, frost dates and crops by region
We worked out the season of 14 cities of Ireland from ten years of weather: the frost-free season lasts from 227 days in Sligo to 312 days in Bray. The last spring frost comes first in Bray (around 29 January) and last in Sligo (around 8 April).
Climate zones of Ireland
By the days between the last spring frost and the first autumn frost.
| Zone | Cities | Frost-free days | Last spring frost | First autumn frost |
|---|---|---|---|---|
| 270 frost-free days or more | Athlone, Bray | 274 – 312 | 29 January – 25 February | 26 November – 7 December |
| 210–269 frost-free days | Letterkenny, Sligo, Dundalk, Navan, Mullingar, Dublin, Galway, Limerick, Kilkenny, Tralee, Waterford, Cork | 227 – 262 | 3 March – 8 April | 20 November – 28 November |
How the regions of Ireland differ
Splitting the cities in two — north (Letterkenny, Sligo, Dundalk and 4 more) and south (Galway, Bray, Limerick and 4 more): the last spring frost comes about 11 days later in the north; the frost-free season is about 243 days in the north and 253 days in the south.
Tralee is the wettest of these cities with 1,485 mm a year, Navan the driest with 958 mm. In none of these cities does a month average below 0 °C at night.
Which crops suit which part of Ireland
Season long enough: the days from planting to the first autumn frost cover the days to the first harvest on the plant card. 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 | Season long enough | Tight or too short |
|---|---|---|---|
| Tomato | 28 May (Bray) – 17 August (Bray) | all 14 | — |
| Cucumber | 20 June (Bray) – 22 September (Bray) | all 14 | — |
| Bell Pepper, Eggplant | 20 June (Bray) – 17 August (Bray) | all 14 | — |
| Zucchini | 20 June (Bray) – 20 September (Bray) | all 14 | — |
| Pumpkin | 20 June (Bray) – 12 August (Bray) | all 14 | — |
| Watermelon | 20 June (Bray) – 28 August (Bray) | all 14 | — |
| Peas | 8 January (Bray) – 24 September (Bray) | all 14 | — |
| Garlic, Tulip, Daffodil, Crocus, Hyacinth | Autumn planting: 21 October (Dundalk) – end of December (Letterkenny) | — | — |
Cities of Ireland: weather in numbers
| City | Frost-free days | Warmest month, day | Coldest month, night | Rain a year | Driest month | Places to buy |
|---|---|---|---|---|---|---|
| Letterkenny | 243 | August, 17.7 °C | January, 2.7 °C | 1,237 mm | April | 4 |
| Sligo | 227 | August, 17.9 °C | January, 2.8 °C | 1,438 mm | April | 3 |
| Dundalk | 245 | July, 19 °C | January, 2.5 °C | 1,013 mm | May | 6 |
| Navan | 237 | July, 19.2 °C | January, 2.6 °C | 958 mm | May | — |
| Mullingar | 249 | July, 19 °C | January, 2.8 °C | 1,028 mm | May | — |
| Athlone | 274 | July, 19 °C | January, 3.3 °C | 1,084 mm | May | 6 |
| Dublin | 231 | July, 18.5 °C | January, 2.3 °C | 1,086 mm | May | 34 |
| Galway | 256 | July, 18.6 °C | January, 4 °C | 1,354 mm | May | 11 |
| Bray | 312 | July, 19.5 °C | January, 4.3 °C | 1,064 mm | May | — |
| Limerick | 253 | July, 18.9 °C | January, 3.3 °C | 1,361 mm | April | 10 |
| Kilkenny | 227 | July, 18.9 °C | January, 2.2 °C | 1,069 mm | May | 22 |
| Tralee | 244 | August, 18.2 °C | January, 3.8 °C | 1,485 mm | May | 7 |
| Waterford | 262 | July, 19.2 °C | January, 3.2 °C | 1,170 mm | May | 14 |
| Cork | 232 | July, 19.1 °C | January, 3.2 °C | 1,209 mm | June | 19 |
ERA5 2016–2025 via Open-Meteo, 25 km grid cell of each city; dates by the Greenly calendar and the plant cards.
