First Frost Date Montreal — October 7 (Zone 5b)
First frost date Montreal: October 7 for the island (Zone 5b). Laval and the South Shore frost a few days earlier; the Laurentian foothills frost in late September. Harvest deadlines, borough breakdown, season extension.
Updated June 2026 · Environment and Climate Change Canada normals (1991–2020)
First frost date Montreal 2026: October 7 for the Island of Montreal (Zone 5b). Urban core (Plateau, Ville-Marie, Rosemont): October 10–15 thanks to the heat island. Laval, South Shore: October 3–10. Laurentian foothills (Saint-Jérôme, Sainte-Agathe): September 15–October 1. Harvest tomatoes, peppers, basil, and squash before mid-September frost watches begin off-island; kale, carrots, and Brussels sprouts improve after frost and can stay in. Historical range: September 20 (earliest) to October 25 (latest). Source: Environment and Climate Change Canada climate normals (1991–2020).
Main planting window in Montréal
- Transplant tomatoes, peppers, basil, eggplant, cucumbers, and squash — overnight lows are warm enough.
- Direct-sow beans, corn, and zucchini.
- Mulch around new transplants to lock in soil moisture and warmth.
Come back next week: By June 29 you'll be in maintenance mode — succession sowing and watering deeply through summer.
🍂 Montreal Frost Dates at a Glance
Historical Average and Range
The first frost date for Montreal — October 7 for the island — is the 50th-percentile historical average drawn from Environment and Climate Change Canada climate normals for the 1991–2020 reference period. Roughly half of recent autumns have stayed frost-free past October 7, and half have frosted before it. The full range runs from about September 20 (earliest first frost in modern island records) to October 25 (latest) — a five-week window that rewards watching the forecast over trusting the calendar.
Two geographic forces shape Montreal's fall frost. The first is the urban heat island: the densely built central boroughs (Plateau, Ville-Marie, Rosemont, Villeray) hold several degrees of warmth on clear nights, often pushing the first frost to mid-October while off-island gardens have already been hit. The second is the St. Lawrence and Rivière des Prairies, whose water moderates the island's edges. Move 30 km north into the Laurentian foothills and both effects vanish — Saint-Jérôme frosts a week or more before downtown, and the ski-country towns can frost before September ends.
Montreal also reliably enjoys the gap between first frost and first hard freeze (−4°C or colder). The first light frost around October 7 is usually followed by two to four mild weeks — often including a stretch of warm été des Indiens days — before the real freeze ends the season in late October or early November. Gardeners who cover tender crops through the first one or two cold nights harvest deep into October most years.
First Frost by Borough, Suburb, and Region
Fall frost reaches Greater Montreal from the north and west. The Laurentian foothills frost first, then the off-island crowns, then the island, with the dense central boroughs last. On clear, calm nights cold air drains downslope and pools in low-lying spots — a garden at the bottom of a hill in Laval can frost ten days before a Plateau balcony.
| Borough / Municipality | Avg. First Frost | Zone | Notes |
|---|---|---|---|
| Plateau, Ville-Marie, Rosemont | Oct 10–15 | 5b/6a | Urban heat island; latest frost in the metro |
| NDG, Côte-des-Neiges, Outremont | Oct 8–12 | 5b | Mount Royal slopes; mature canopy moderates |
| West Island (Pointe-Claire, DDO, Kirkland) | Oct 5–8 | 5b | Less heat island; lake-edge lots slightly later |
| Laval | Oct 3–7 | 5b | Off-island; low-lying pockets frost earlier |
| Longueuil, Brossard, Saint-Lambert | Oct 5–10 | 5b | Inner South Shore; close to island timing |
| Saint-Jean-sur-Richelieu | Oct 3–8 | 5b | Richelieu Valley; open farmland radiates fast |
| Vaudreuil-Dorion | Oct 3–7 | 5b | Off-island west; lake edges slightly later |
| Mirabel, Saint-Jérôme | Sept 25–Oct 1 | 5a | Laurentian approach; a week ahead of the island |
| Sainte-Agathe, Saint-Sauveur (Laurentians) | Sept 15–25 | 4a/4b | Elevation; valley-bottom frost pockets earlier still |
| Sherbrooke (Eastern Townships) | Sept 20 | 4b/5a | Higher terrain; see the Sherbrooke frost guide (FR) |
| Trois-Rivières | Sept 28 | 5a | St. Lawrence midpoint between Montreal and Quebec City |
Dates derived from ECCC climate normals (1991–2020) and station-level observations from Montreal-Trudeau (YUL), McTavish (downtown), Mirabel, and Saint-Hubert. Treat as historical averages; actual frost dates vary year to year by up to 2 weeks.
What to Harvest Before Montreal's First Frost — and What to Leave In
The October 7 first frost splits the fall garden into two lists. Tender crops are finished by the first frost of any intensity — wrap up that harvest as frost watches begin in late September. Hardy crops shrug off light frost, and several genuinely improve after a few cold nights convert starches to sugar.
⚠️ Harvest before first frost
- Tomatoes: pick all fruit, even green — ripen indoors at 18–21°C
- Basil: before nights hit 5°C — cold damages it pre-frost
- Peppers, eggplant: killed by the lightest frost
- Cucumbers, zucchini, beans: final picking by late September
- Winter squash, pumpkins: cut with 5–8 cm stem, cure 10 days warm
- Potatoes: dig after tops die back, before a hard freeze
❄️ Leave in — improves after frost
- Kale, Brussels sprouts: sweeter after 2–3 frosts; harvest into November
- Carrots, parsnips: mulch heavily and dig until the ground freezes
- Leeks, cabbage: stand through repeated light frosts
- Spinach, arugula: keep producing under row cover to November
- Swiss chard: survives to about −4°C uncovered
- Garlic: plant it early-to-mid October — frost is its friend
How to Extend the Season Past Montreal's First Frost
Montreal's first frost is usually one or two clear, calm radiation-frost nights followed by another stretch of mild weather — often a genuine été des Indiens. Protecting tender crops through those first cold nights is the single highest-return move in the Quebec fall garden.
Row cover on frost-watch nights
Spun-bonded fabric (Reemay, Agribon) draped over tomatoes, peppers, and greens before sunset traps ground heat and protects to about −3°C — more than the typical first frost delivers. Cover for the 2–3 cold nights in early October and the harvest usually continues to month's end. Weight the edges with stones or soil; remove once morning temperatures clear 5°C.
Exploit the heat island and brick walls
Central Montreal's triplex courtyards, balconies, and brick-walled ruelles vertes hold 2–3°C of extra overnight warmth on frost nights. Container tomatoes and herbs moved against a south-facing brick wall in the Plateau routinely produce two weeks longer than open suburban beds. If you garden off-island, the same principle applies: the warmest microclimate is against the house, not at the back of the yard.
Cold frames and low tunnels for fall greens
A cold frame or low tunnel (hoops + greenhouse plastic) keeps spinach, lettuce, mâche, and Asian greens producing through November in most Montreal years. Sow hardy greens in mid-to-late August so plants reach full size before light fades. Overwintered spinach under cover restarts in April — the earliest harvest of the new season, weeks before anything direct-sown.
Then switch to planting mode
The first frost is Montreal's signal to plant, not just to harvest: garlic goes in early-to-mid October (2–3 weeks before the ground freezes), and spring bulbs — tulips, daffodils, alliums — plant right up until the soil is frozen solid. By mid-November, day length below 10 hours stops growth regardless of temperature; harvest what's mature and let covered greens hold for winter picking.
A lightweight floating row cover you drape straight over beds on frost-watch nights — the simplest way to act on the advice above. Buys several degrees of protection and routinely adds 2–3 weeks of harvest at the fall end of the season.
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How Montreal's First Frost Compares to Other Canadian Cities
Montreal sits in the middle of the Canadian fall-frost range — nearly a month behind Toronto, but two to three weeks ahead of the Prairie cities and the Quebec hinterland.
| City | First Frost | Zone | Season | vs. Montreal |
|---|---|---|---|---|
| Vancouver | Nov 30 | 8b | ~260 days | 54 days later |
| Toronto | Nov 1 | 6b | ~197 days | 25 days later |
| Halifax | Oct 18 | 6a | ~161 days | 11 days later |
| Ottawa | Oct 12 | 5a | ~155 days | 5 days later |
| Montreal | Oct 7 | 5b | ~150 days | — |
| Quebec City | Sept 28 | 5a | ~134 days | 9 days earlier |
| Edmonton | Sept 23 | 4a | ~132 days | 14 days earlier |
| Winnipeg | Sept 20 | 3a | ~118 days | 17 days earlier |
| Saskatoon | Sept 12 | 3b | ~110 days | 25 days earlier |
Common Questions about Montreal's First Frost
When should I pick my green tomatoes in Montreal?
When the forecast shows an overnight low of 4°C or below under clear skies — typically in the last week of September or first week of October. Pick everything showing colour plus full-size green fruit; they ripen indoors over 2–4 weeks at room temperature. Or cover the plants with row cover through the first frost nights — Montreal's mild mid-October stretch usually rewards it with two more weeks of on-vine ripening.
Why did my Laval garden frost when downtown Montreal didn't?
The urban heat island. Central Montreal's dense brick and asphalt holds several degrees of warmth on clear, calm nights — exactly the nights radiation frost forms. Laval, the South Shore, and off-island suburbs lack that thermal mass, and low-lying yards collect the cold air that drains downslope after sunset. The difference is routinely 3–5°C on frost nights, which translates to a first frost 5–10 days earlier off-island than in the Plateau.
When should I plant garlic in Montreal?
Early-to-mid October — right around first frost. The target is 2–3 weeks before the ground freezes solid, giving cloves time to root without sprouting above ground. Hardneck varieties (Music, Russian Red) handle Quebec winters reliably under a 10 cm mulch of straw or shredded leaves. See the when to plant garlic guide for depth and spacing.
When is Montreal's last spring frost?
May 9 for the island average. Together with the October 7 first fall frost, Montreal gets roughly 150 frost-free days — comfortable for full-season tomatoes, peppers, and squash. The full spring breakdown — borough dates, the heat-island effect, what to plant when — is on the Last Frost Date Montreal page (also available in French).
Where does this frost date data come from?
Environment and Climate Change Canada (ECCC) climate normals for the 1991–2020 reference period, supplemented by station-level observations from Montreal-Trudeau International Airport (YUL), McTavish (downtown), Mirabel, and Saint-Hubert. The October 7 average reflects the island stations; borough and suburb dates are adjusted for the urban heat island, elevation, and distance from the St. Lawrence.
📍 Related Montréal Garden Guides
Plan the Whole Montreal Season
The Montreal planting guide turns the May 9 – October 7 frost-free window into a month-by-month schedule for 25+ vegetables — including fall succession sowings timed to the first frost.