Growing Degree Days by Canadian City
Growing degree days (GDD) by Canadian city — the growing-season heat budget that frost-free day counts miss. A free, sourced table of base‑5 & base‑10 GDD for 19 cities, taken directly from Environment and Climate Change Canada's climate normals for both the 1981–2010 and 1991–2020 reference periods, same station in each.
At a glance: A growing degree day counts accumulated warmth above a base temperature — base 5 °C for most temperate plants, base 10 °C for heat-lovers like corn and tomatoes. Of the 19 cities here, Windsor has the most growing-season heat (2,718.1 GDD base 5, 1991–2020) and St. John's the least (1,309.9). Comparing the two climate normals same-station, base-5 GDD rose in 15 cities and fell in 4 — growing-season heat is not rising uniformly across Canada. Free to cite with a link to this page.
📥 Download the dataset
All 19 cities — station, Climate ID, base-5 & base-10 GDD for both normals, and the change — as a free CSV.
Download CSV →📝 How to cite this data
Growing degree days (base 5 & 10 °C) by Canadian city, compiled by GrowersGuide.ca from Environment and Climate Change Canada Canadian Climate Normals (1981–2010 & 1991–2020).
GDD by City — Current Normal (1991–2020)
Annual growing degree days from ECCC's most recent climate normal, warmest first. Base 5 is the all-round season measure; base 10 is the heat that warm-season crops actually use. The change column is the same-station difference from the previous (1981–2010) normal.
| City | GDD base 5 | GDD base 10 | Base-5 change vs 1981–2010 |
|---|---|---|---|
| Windsor (ON) | 2,718.1 | 1,660.7 | +29.9 |
| Toronto (ON) | 2,387.2 | 1,405.7 | +97 |
| London (ON) | 2,285.0 | 1,316.5 | +74.2 |
| Montreal (QC) | 2,247.0 | 1,317.2 | +62.5 |
| Vancouver (BC) | 2,205.0 | 994.1 | +28.2 |
| Ottawa (ON) | 2,179.7 | 1,263.5 | +37.9 |
| Victoria (BC) | 2,055.5 | 860.3 | +46.8 |
| Kelowna (BC) | 2,010.3 | 1,055.3 | +20.9 |
| Halifax (NS) | 1,860.9 | 965.6 | +54.1 |
| Fredericton (NB) | 1,841.8 | 980.5 | +38.3 |
| Winnipeg (MB) | 1,813.6 | 1,016.2 | -7.1 |
| Quebec City (QC) | 1,801.7 | 967.3 | +68.8 |
| Sudbury (ON) | 1,779.8 | 967.0 | +31 |
| Charlottetown (PE) | 1,739.1 | 898.8 | +31.6 |
| Regina (SK) | 1,676.1 | 883.3 | -35.9 |
| Saskatoon (SK) | 1,619.3 | 837.1 | -26.4 |
| Calgary (AB) | 1,447.8 | 649.7 | +0.6 |
| Edmonton (AB) | 1,352.3 | 604.9 | -11 |
| St. John's (NL) | 1,309.9 | 581.8 | +23 |
How to Use These Numbers
- Compare cities honestly. Two cities can share a frost-free length yet differ sharply in heat. Frost-free days tell you how long; GDD tells you how warm — the missing half of the picture for anyone choosing heat-loving varieties.
- Match a variety to your budget. Seed catalogues increasingly list GDD-to-maturity (or corn heat units). If a variety needs more heat than your city's seasonal total, pick a shorter-season variety or add season extension — row cover, black plastic mulch, a low tunnel.
- Watch base 10 for the heat-lovers. Melons, long-season peppers, flint/dent corn and sweet potatoes run on base-10 heat. A thin base-10 total is the real reason a cool-summer city struggles with them — not the calendar.
- Know what this figure is (and isn't). These are climate-normal annual totals — a typical yearly heat budget for comparing locations and judging what class of crop is viable. They are not a live, day-by-day seasonal counter; to track this season's accumulation for timing a specific job, you work from daily temperatures. Use these normals for the strategic choice, your season for the tactical one.
Did Growing-Season Heat Increase? The Same-Station Shift
Because every city here is measured at the same station in both climate normals, the difference between periods is a like-for-like signal, not an artefact of a moved thermometer. Across the 19 cities, base-5 GDD rose in 15 and fell in 4, a mean of +29.7 GDD. The gains cluster in the east and on the coasts; several Prairie stations recorded fewer degree days in the newer normal. Growing-season heat is not moving in one direction across the country.
| City | Base 5 1981–2010 → 1991–2020 |
Δ5 | Base 10 1981–2010 → 1991–2020 |
Δ10 |
|---|---|---|---|---|
| Toronto (ON) | 2,290.2 → 2,387.2 | +97 | 1,324.6 → 1,405.7 | +81.1 |
| London (ON) | 2,210.8 → 2,285.0 | +74.2 | 1,256.3 → 1,316.5 | +60.2 |
| Quebec City (QC) | 1,732.9 → 1,801.7 | +68.8 | 917.5 → 967.3 | +49.8 |
| Montreal (QC) | 2,184.5 → 2,247.0 | +62.5 | 1,260.0 → 1,317.2 | +57.2 |
| Halifax (NS) | 1,806.8 → 1,860.9 | +54.1 | 921.9 → 965.6 | +43.7 |
| Victoria (BC) | 2,008.7 → 2,055.5 | +46.8 | 820.6 → 860.3 | +39.7 |
| Fredericton (NB) | 1,803.5 → 1,841.8 | +38.3 | 949.0 → 980.5 | +31.5 |
| Ottawa (ON) | 2,141.8 → 2,179.7 | +37.9 | 1,230.6 → 1,263.5 | +32.9 |
| Charlottetown (PE) | 1,707.5 → 1,739.1 | +31.6 | 871.5 → 898.8 | +27.3 |
| Sudbury (ON) | 1,748.8 → 1,779.8 | +31 | 943.6 → 967.0 | +23.4 |
| Windsor (ON) | 2,688.2 → 2,718.1 | +29.9 | 1,634.0 → 1,660.7 | +26.7 |
| Vancouver (BC) | 2,176.8 → 2,205.0 | +28.2 | 965.7 → 994.1 | +28.4 |
| St. John's (NL) | 1,286.9 → 1,309.9 | +23 | 559.0 → 581.8 | +22.8 |
| Kelowna (BC) | 1,989.4 → 2,010.3 | +20.9 | 1,035.4 → 1,055.3 | +19.9 |
| Calgary (AB) | 1,447.2 → 1,447.8 | +0.6 | 650.5 → 649.7 | -0.8 |
| Winnipeg (MB) | 1,820.7 → 1,813.6 | -7.1 | 1,017.7 → 1,016.2 | -1.5 |
| Edmonton (AB) | 1,363.3 → 1,352.3 | -11 | 610.8 → 604.9 | -5.9 |
| Saskatoon (SK) | 1,645.7 → 1,619.3 | -26.4 | 860.8 → 837.1 | -23.7 |
| Regina (SK) | 1,712.0 → 1,676.1 | -35.9 | 913.0 → 883.3 | -29.7 |
Companion analysis of the frost-free season length over the same two normals is in the Frost-Free Season Shift study — heat (GDD) and season length don't always move together, which is the interesting part.
Methodology & Sources
- Source. Every value is Environment and Climate Change Canada's published annual Degree-Days above 5 °C and above 10 °C, from the Canadian Climate Normals, for the 1981–2010 and 1991–2020 reference periods.
- Same-station rule. For each city the two periods are read from the same long-record station, matched by Climate ID (shown in the CSV). A city is included only if that station carries a published annual value in both periods for both thresholds; where it does not, the city is flagged and skipped — never substituted with a nearby station. Thunder Bay, ON is the current worked example: its principal normals station publishes no degree-day section, and it is the only Thunder Bay station in the normals, so it is excluded rather than swapped for a different site.
- Completeness codes. The CSV carries ECCC's per-period completeness code (A = meets the WMO "3-and-5" rule; B = ≥25 years; C = ≥20 years; D = ≥15 years). The 1991–2020 normal often carries a C or D where 1981–2010 was an A, because fewer complete years were available at some stations in the newer window — a real limitation, disclosed rather than hidden.
- Base 5 vs base 10. Both are ECCC-published. Base 5 °C approximates the threshold for cool-season growth; base 10 °C isolates the heat that warm-season crops use. We publish both rather than pick one.
- Live-computed. The at-a-glance figures, warmest/coolest city, rose/fell counts and mean shift on this page are computed from the downloadable CSV on every load — nothing is hand-typed, so the page can never disagree with the data.
For researchers, master gardeners, societies & educators
This table is free to quote and republish — in newsletters, society bulletins, extension handouts, coursework or your own site — with credit to GrowersGuide.ca and a link to this page, and a credit to Environment and Climate Change Canada as the primary source. Want a city added, or the same base-5/base-10 pull for another long-record station? Tell us: zusashicanada@gmail.com.
Every station added follows the same rule — same Climate ID in both periods, or it doesn't go in.
Use of This Data
The compiled dataset on this page is free to use with attribution to GrowersGuide.ca (a link to this page is sufficient) and to Environment and Climate Change Canada as the primary data source. Provided as-is, without warranty; degree-day normals describe typical conditions and any single season will differ — verify against your local station and conditions before making planting decisions.