Last Frost Date Moncton — May 15 (Zone 5b)
Last frost date Moncton: May 15 for the urban core (Zone 5b). Greater Moncton tri-city (Dieppe, Riverview) shares the date; Shediac and the Acadian coast run 2–4 days earlier; inland NB (Salisbury, Sussex) runs 2–7 days later. Bay of Fundy moderation, historical range, frost protection.
Updated May 2026 · Environment and Climate Change Canada normals (1991–2020)
Last frost date Moncton 2026: May 15 for the urban core (downtown, North End, Lewisville) — hardiness Zone 5b. Greater Moncton (Dieppe, Riverview): May 14–16. Acadian coast (Shediac, Cap-Pelé, Bouctouche): May 11–14. Sackville NB / Tantramar: May 13–17. Inland NB (Salisbury, Sussex): May 17–22. Wait until May 25–June 1 to transplant tomatoes, peppers, basil, and other frost-sensitive crops. Historical range: late April (earliest) to early June (latest). Source: Environment and Climate Change Canada climate normals (1991–2020).
Main planting window in Moncton
- 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 July 5 you'll be in maintenance mode — succession sowing and watering deeply through summer.
❄️ Moncton Frost Dates at a Glance
Planning the other end of the season? See First Frost Date Moncton — September 28: harvest deadlines, neighbourhood breakdown, and season extension.
Last Frost Date Moncton — Historical Average
The last frost date for Moncton — May 15 for the urban core — is the 50th-percentile historical average drawn from Environment and Climate Change Canada climate normals for the 1991–2020 reference period. In plain terms: roughly half of recent years have seen Moncton's last spring frost before May 15, and half after. It is a planning anchor with meaningful year-to-year variation because Moncton sits at the intersection of three different climate influences — the Bay of Fundy to the south, the Northumberland Strait to the east, and the continental interior of New Brunswick to the north.
The full historical range tells the rest of the story. The earliest last spring frost recorded in modern records for Moncton's urban core is around April 25; the latest is around June 5. That's a 40-day window — wider than southern Ontario because the Maritimes get more variable spring weather from Atlantic storm tracks. A warm March-April can pull the last frost forward by two weeks; a cold spring with persistent low pressure off the Gulf of St. Lawrence can push it into early June.
The 1991–2020 normals replaced the older 1981–2010 set in 2021. Compared to the older period, Moncton's average last frost has shifted about 3–5 days earlier due to gradual warming. ECCC updates its 30-year normals every decade, so the May 15 figure will hold as the official average until the next update around 2031.
Last Frost by Greater Moncton Community and Surrounding Area
Frost dates across Greater Moncton and the surrounding area vary by 7–10 days based on proximity to the Bay of Fundy, the Northumberland Strait, and elevation. The Petitcodiac River and tidal bore provide some urban-area moderation. The Acadian coast benefits from the warmer (but shallower) Northumberland Strait. Inland communities lose ocean moderation and behave more like interior Maine.
| Community | Last Frost | Zone |
|---|---|---|
| Shediac, Cap-Pelé, Bouctouche (Acadian coast) | May 11–14 | 5b/6a |
| Sackville NB / Tantramar marsh | May 13–17 | 5b |
| Dieppe | May 14–16 | 5b |
| Riverview | May 14–16 | 5b |
| Moncton urban core (downtown, North End, Lewisville) | May 15 | 5b |
| Memramcook | May 14–17 | 5b |
| Salisbury, Hampton | May 17–20 | 5a/5b |
| Sussex (Kennebecasis valley) | May 17–22 | 5a/5b |
| Petitcodiac, Elgin (inland) | May 18–25 | 5a |
Dates derived from ECCC climate normals (1991–2020) plus station-by-station observations across Greater Moncton, the Acadian coast, and inland southern New Brunswick.
How to Protect Plants from a Late Moncton Frost
A late frost after May 15 happens roughly 1 year in 5 in Moncton's urban core, more often in Salisbury, Sussex, and other inland communities. Maritime late frosts are usually -1 to -3°C, accompanied by cold Atlantic rain or wet snow rather than the dry radiation frosts of the Prairies. Four protection methods that work for Moncton gardens:
- Floating row cover (Reemay, Agribon): draped over transplants in the evening, removed in the morning. Protects to about -3°C and is the Maritime workhorse — available at Atlantic-coast garden centres (Halifax Seed, Country Stores), Home Hardware, and Canadian Tire.
- Cloches and individual covers: inverted plastic milk jugs (4 L), commercial cloches, or 2 L pop bottles cut in half work for 5–10 individual tomato or pepper transplants on forecast frost nights.
- Heavy mulch: 5–10 cm of straw, salt-marsh hay, or shredded leaves around transplants insulates roots and buffers overnight temperature swings by 2–3°C.
- Warm microclimates: plant tender crops against a south-facing fence, a brick wall, or in a Tantramar dyked field where marsh moderation buys 3–5 days. Avoid frost pockets at the base of hills.
The golden rule for Moncton: never transplant tomatoes, peppers, basil, beans, or squash if nights below 5°C are forecast within 7 days. The May 15 average is an anchor, not a guarantee — always check the 10-day forecast from Environment Canada before transplanting.
What to Plant Before vs. After Moncton's Last Frost
❄️ Before May 15 (frost-tolerant)
- Direct sow mid-April: peas, spinach, radishes, lettuce, arugula, kale
- Direct sow late April: carrots, beets, Swiss chard, parsnips, turnips
- Transplant late April/early May: broccoli, cabbage, cauliflower, kohlrabi
- Transplant early May: onions, leeks, hardy herbs
- Plant fall (mid-October): hardneck garlic — overwinters reliably with snow cover
⚠️ After May 25 (frost-sensitive)
- Tomatoes: transplant May 25–June 1 (60–75 day varieties)
- Peppers: transplant June 1–5 (soil at 15°C)
- Basil: June 1 minimum — cold damages it permanently
- Beans, cucumbers, squash: direct sow late May/early June
- Melons, eggplant: marginal in Zone 5b — pick short-season varieties only
How Moncton's Frost Date Compares to Other Canadian Cities
Moncton's May 15 last frost is right in the middle of the Canadian range — later than Halifax (May 10) and Toronto (April 20) but earlier than Montreal (May 9 inland, but Greater Moncton's Zone 5b is similar), Edmonton (May 14), Calgary (May 23), and Winnipeg (May 25). The Maritime climate gives Moncton a meaningful advantage over the Prairies: shorter winters, cooler but more predictable summers, and reliable snow cover that protects perennials.
| City | Last Frost | Zone | Compared to Moncton |
|---|---|---|---|
| Halifax | May 10 | 6a | 5 days earlier |
| Charlottetown PEI | May 14 | 6a | 1 day earlier |
| Moncton | May 15 | 5b | — |
| Fredericton | May 17 | 5b | 2 days later |
| Saint John NB | May 8 | 6a | 7 days earlier (Bay of Fundy) |
| Montreal | May 9 | 5b | 6 days earlier |
| Toronto | April 20 | 6b | 25 days earlier |
Common Questions about Moncton's Last Frost
When can I safely transplant tomatoes in Moncton?
May 25–June 1 in Greater Moncton (Dieppe, Riverview), May 23–28 along the Acadian coast (Shediac), and June 1–5 inland (Sussex, Salisbury). Tomatoes need both frost-free conditions and warm soil (above 12°C at 5 cm depth). Moncton's 136-day growing season is long enough for most full-season varieties, but stick to 65–75 day cultivars (Bush Beefsteak, Manitoba, Scotia) for reliable maturity before the September 28 first fall frost. Harden off transplants 7–10 days before setting them out.
Why does Moncton freeze later than Halifax and Saint John?
Halifax and Saint John both sit directly on the ocean — Halifax on the open Atlantic, Saint John on the Bay of Fundy. The proximity gives them stronger maritime moderation and pushes their last frost earlier (May 10 and May 8 respectively). Moncton sits inland from the Bay of Fundy with the Petitcodiac River providing only modest moderation, and it has slight elevation. The result is a 5–7 day later last frost than the immediate ocean cities, even though Moncton is in the same general latitude band. The Acadian coast (Shediac, Cap-Pelé) is closer to Halifax's pattern thanks to Northumberland Strait proximity.
What hardiness zone is Greater Moncton?
Moncton's urban core (downtown, North End, Lewisville), Dieppe, and Riverview are all in Zone 5b under the Canadian Plant Hardiness Zone system. The Acadian coast (Shediac, Cap-Pelé, Bouctouche) sits in Zone 5b/6a thanks to Northumberland Strait moderation. Sackville NB and Tantramar are Zone 5b with salt-marsh microclimate effects. Inland NB (Salisbury, Sussex, Petitcodiac) drops to Zone 5a/5b. A Zone 5 plant will survive reliably anywhere in the region; Zone 6 plants are a gamble inland but reliable on the immediate coast.
When is the first fall frost in Moncton?
Around September 28 for Moncton's urban core. Inland communities (Sussex, Petitcodiac) can frost by mid-September. The Acadian coast holds frost off until early October. The fall frost arrives faster and harder than the spring frost — a clear cold late-September night can drop temperatures to -2°C and end the tomato season overnight. Many Moncton gardeners buy themselves 7–10 extra harvest days by covering tomatoes and peppers with row cover on forecast frost nights through early October.
📍 Related Moncton Garden Guides
Plan Your Moncton Garden Season
Combine Moncton's May 15 frost date with your exact postal code in the frost calculator and the seed-starting calculator to build a precise planting schedule for Greater Moncton's 136-day Zone 5b season.