GreenlyFrost dates and when to plant in Auvergne-Rhône-Alpes
France
In Auvergne-Rhône-Alpes the last spring frost comes between 18 March (Valence) and 5 May (Grenoble) — the median of 2016–2025 in 7 cities. The first autumn frost comes between 25 October (Grenoble) and 25 November (Lyon). The frost-free season lasts 173–248 days. Tomato: plant out into open ground 1 May – 5 August, earliest in Valence, latest in Lyon.
Frost dates by city in Auvergne-Rhône-Alpes
| City | Last spring frost | First autumn frost | Frost-free days | Climate zone | Tomato: window |
|---|---|---|---|---|---|
| Valence | 18 March | 21 November | 248 | 210–269 frost-free days | 1 May – 1 August |
| Lyon | 26 March | 25 November | 244 | 210–269 frost-free days | 2 May – 5 August |
| Chambéry | 5 April | 20 November | 229 | 210–269 frost-free days | 13 May – 31 July |
| Saint-Étienne | 13 April | 17 November | 218 | 210–269 frost-free days | 30 May – 28 July |
| Annecy | 15 April | 14 November | 213 | 210–269 frost-free days | 2 June – 25 July |
| Clermont-Ferrand | 15 April | 12 November | 211 | 210–269 frost-free days | 6 June – 23 July |
| Grenoble | 5 May | 25 October | 173 | 150–209 frost-free days | 20 June – 5 July |
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 Auvergne-Rhône-Alpes: 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 | 1 May (Valence) – 5 August (Lyon) |
| Cucumber | 27 May (Lyon) – 10 September (Lyon) |
| Bell Pepper, Eggplant | 27 May (Lyon) – 5 August (Lyon) |
| Zucchini | 27 May (Lyon) – 8 September (Lyon) |
| Pumpkin | 27 May (Lyon) – 31 July (Lyon) |
| Watermelon | 27 May (Lyon) – 16 August (Lyon) |
| Peas | 25 February (Valence) – 12 September (Lyon) |
| Garlic, Tulip, Daffodil, Crocus, Hyacinth | Autumn planting: 25 September (Grenoble) – end of December (Lyon) |
Weather by month in Auvergne-Rhône-Alpes
Across the 7 cities the warmest month is August (average days 22.5 … 29.4 °C) and the coldest January (average nights -5.1 … 1 °C). 4 of the 7 cities have months with nights below 0 °C on average; the longest such winter is in Grenoble (November–March).
| Month | Day, °C | Night, °C | Rain, mm |
|---|---|---|---|
| January | 2.9 … 8 °C | -5.1 … 1 °C | 76 |
| February | 6.4 … 11.1 °C | -2.9 … 2.3 °C | 50 |
| March | 8.9 … 14.1 °C | -1.4 … 3.9 °C | 81 |
| April | 11.9 … 17.4 °C | 1.1 … 6.8 °C | 80 |
| May | 14.9 … 20.9 °C | 5 … 10.6 °C | 117 |
| June | 19.9 … 26.8 °C | 10.1 … 15.8 °C | 113 |
| July | 22.1 … 29.3 °C | 11.7 … 17.5 °C | 68 |
| August | 22.5 … 29.4 °C | 11.7 … 17.4 °C | 64 |
| September | 18 … 24.3 °C | 7.7 … 13.6 °C | 71 |
| October | 14.1 … 19 °C | 4.3 … 9.8 °C | 111 |
| November | 7 … 12.1 °C | -1 … 4.9 °C | 99 |
| December | 3.7 … 8.8 °C | -3.9 … 2 °C | 90 |
Day and night: the lowest … highest monthly average among the cities; rain: the middle city (ERA5 via Open-Meteo).
