GreenlyFrost dates and when to plant in Quebec
Canada
In Quebec the last spring frost comes between 27 April (Montreal) and 14 May (Saguenay) — the median of 2016–2025 in 6 cities. The first autumn frost comes between 22 October (Saguenay) and 1 November (Gatineau). The frost-free season lasts 161–188 days. Tomato: plant out into open ground 21 May – 12 July, earliest in Montreal, latest in Montreal.
Frost dates by city in Quebec
| City | Last spring frost | First autumn frost | Frost-free days | Climate zone | Tomato: window |
|---|---|---|---|---|---|
| Montreal | 27 April | 1 November | 188 | 150–209 frost-free days | 21 May – 12 July |
| Trois-Rivières | 29 April | 29 October | 183 | 150–209 frost-free days | 25 May – 9 July |
| Gatineau | 30 April | 1 November | 185 | 150–209 frost-free days | 27 May – 12 July |
| Quebec City | 5 May | 28 October | 176 | 150–209 frost-free days | 27 May – 8 July |
| Sherbrooke | 8 May | 27 October | 172 | 150–209 frost-free days | 27 May – 7 July |
| Saguenay | 14 May | 22 October | 161 | 150–209 frost-free days | 10 June – 2 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 Quebec: 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 | 21 May (Montreal) – 12 July (Montreal) |
| Cucumber | 30 May (Montreal) – 17 August (Montreal) |
| Bell Pepper, Eggplant | 30 May (Montreal) – 12 July (Montreal) |
| Zucchini | 30 May (Montreal) – 15 August (Montreal) |
| Pumpkin | 30 May (Montreal) – 8 August (Saguenay) |
| Watermelon | 30 May (Montreal) – 23 July (Montreal) |
| Peas | 6 April (Montreal) – 19 August (Montreal) |
| Garlic, Tulip, Daffodil, Crocus, Hyacinth | Autumn planting: 22 September (Saguenay) – 13 November (Montreal) |
Weather by month in Quebec
Across the 6 cities the warmest month is July (average days 24.2 … 27 °C) and the coldest January (average nights -16.3 … -12 °C). Every city averages below 0 °C at night in November–March.
| Month | Day, °C | Night, °C | Rain, mm |
|---|---|---|---|
| January | -8 … -3.5 °C | -16.3 … -12 °C | 77 |
| February | -6.7 … -1.2 °C | -15.9 … -11.3 °C | 79 |
| March | -0.4 … 3.8 °C | -9.3 … -5.6 °C | 86 |
| April | 6.4 … 11.3 °C | -2.8 … 1.2 °C | 106 |
| May | 15.9 … 19.4 °C | 4.4 … 8.7 °C | 95 |
| June | 21.7 … 24.4 °C | 11.4 … 14.9 °C | 127 |
| July | 24.2 … 27 °C | 14.8 … 18.3 °C | 136 |
| August | 23.1 … 25.7 °C | 14.1 … 17.3 °C | 132 |
| September | 18.9 … 21.7 °C | 10 … 13.4 °C | 77 |
| October | 11.9 … 14.9 °C | 4.4 … 7.5 °C | 120 |
| November | 2.5 … 5.9 °C | -3.7 … -0.4 °C | 91 |
| December | -4.8 … -0.5 °C | -12.7 … -7.8 °C | 90 |
Day and night: the lowest … highest monthly average among the cities; rain: the middle city (ERA5 via Open-Meteo).
